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Air^ Water^ and Food

FROM A SANITARY STANDPOINT

ALPHEUS G. WOODMAN and JOHN F. NORTON

Associate Professor of Assistant Professor of

Food A nalysis Chetnistry of Sanitation

MASSACHl,'SKTTS INSTITUTE OF TECHNOLOGY

" These cannot be taken as sufficient ... in these times when
every word spoken finds at once a reidy doubter, if not an opponent.
They are, however, specimens, and will serve to make comparisons
in time to come." — Angus Smith.

" The ideal scientific mind, therefore, must always be held in a
state of balance which the slightest new evidence may change in one
direction or another. It is in a constant state of skepticism, know-
ing full well that nothing is certain." — Henry A. RowIiANO.-i -•

FOURTH EDITION, RRVI5Eri''A^D>,J^>f:iVJiiT'tMN'

TOTAL ISSUE FIVE ^y'ltofu'sAigif. .' ;'.*,*>!

NEW YORK

JOHN WILEY & SONS, Inc.

London: CHAPMAN & HALL, Limited

1914

ELLEN H. RICHARDS and ALPHEUS G. WOODMAN
Copyright, 19 14

ALPHEUS G. WOODMAN and JOHN F. NORTON

Stanbopc jpress

F. H.GILSON COMPANY
BOSTON, U.S.A.

^/3

PREFACE

Since the last edition (1909) of Air, Water, and Food was
published there have been distinct advances in analytical meth-
ods, and a changed point of view has brought about a somewhat
different interpretation of results. This is particularly true
with regard to the relation of air to health and comfort. At the
present time the subject is still in a somewhat transitory state.
In order that the book might remain useful it seemed necessary
to make a careful revision of the whole.

The death of one of the authors, Mrs. Ellen H. Richards,
made a change in authorship necessary. We are indebted to
Prof. R. H. Richards for permission to use any material from
the former edition. While realizing that the book was first
written from a "missionary" standpoint (Mrs. Richards'
strong point), it actually has been used mainly for college and
technical school teaching; consequently the character of part of
the general discussion has been considerably changed.

All of the discussion on air and water has been completely
rewritten, as has the section on milk, the older methods revised,
and numerous additions, to correspond with the latest practice,
made. As in previous editions, these discussions are intended
to be essentially elementary rather than exhaustive.

A. G. W.
J. F. N.

Boston, July, 1914.

2061665

CONTENTS

Chapter Page

I. Three Essentials of Human Existence i

II. Air and Health q

HI. Air: Analytical Methods 21

IV. Water: Its Relation to Health, Its Source and Properties.. 43

V. Safe Water and the Interpretation of Analyses 56

VI. Water: Analytical Methods 69

VII. Food in Relation to Human Life, Definition, Sources, Classes,

Dietaries m

VIII. Adulteration and Sophistication of Food Materials 124

IX. Analytical Methods 135

Appendices 208

Bibliogr.'Vphy 228

AIR, WATER, AND FOOD

CHAPTER I

THREE ESSENTIALS OF HUMAN EXISTENCE

Air, water, and food are three essentials for healthful human
life. Chemical Analysis deals with these three commodities in
their relation to the needs of daily existence: first, as to their
normal composition; second, as to natural variations from the
normal; third, as to artificial variations — those produced
directly by human agency with benevolent intention, or result-
ing from carelessness or cupidity. A large portion of the prob-
lems of public health come under these heads, and a discussion
of them in the broadest sense includes a consideration of engi-
neering questions and of municipal finances. This, however, is
beyond the scope of the present work.

The following pages will deal chiefly with such portions of
the Chemistry of Sanitation as come directly under indi\'idual
control, or which require the education of individuals in order
to make up the mass of public opinion which shall support the
city or state in carrying out sanitary measures.

A notable interest in the subject of individual health as a
means of securing the highest individual capacity both for
work and for pleasure is being aroused as the application of
the principles governing the evolutionary progress of other
forms of Uving matter is seen to extend to mankind.

Will power may guide human forces in most economical
ways, and may concentrate energy upon a focal point so as
to seem to accomphsh superhuman feats, but it cannot create
force out of nothing. There is a law of conservation of human

2 AIR, WATER, AND FOOD

energy. The human body, in order to carry on all its functions
to the best advantage, especially those of the highest thought
for the longest time, must be placed under the best conditions
and must be supplied with clean air, safe water, and good food,
and must be able to appropriate them to its use. The day is
not far distant when a city will be held as responsible for the
purity of the air in its schoolhouses, the cleanliness of the water
in its reservoirs, and the rehability of the food sold in its markets
as it now is for the condition of its streets and bridges. Nor
will the years be many before educational institutions will be
held as responsible for the condition of the bodies as of the
minds of the pupils committed to their care; when a chair of
Sanitary Science will be considered as important as a chair
of Greek or Mathematics; when the competency of the food-
purveyor will have as much weight with intelligent patrons as
the scholarly reputation of any member of the Faculty. Within
a still shorter time will catalogues call the attention of the inter-
ested public to the ventilation of college halls and dormitories,
as well as to the exterior appearance and location.

These results can be brought about only when the students
themselves appreciate the possibilities of increased mental produc-
tion under conditions of decreased friction, such as can be found
only when the requirements of health are perfectly fulfilled.

Of the three essentials, air may well be considered first, al-
though its ofiice is to convert food already taken into heat and
energy. Its exclusion only for a few minutes causes death, and
in quantity used it far exceeds the other two. Again, so im-
portant is the action of air that the quality of food is of far less
consequence when abundant oxygen is present, as in pure air,
than when it is present in lessened quantity, as in air vitiated
by foreign substances.

Individual habit has much to do with the appreciation of
good air, and as our knowledge of the value of an abundance of
this substance in securing great efficiency in the human being
increases, we shall be led to attach more importance to the
sufiSciency of the supply.

THREE ESSENTIALS OF HUMAN EXISTENCE 3

In northern climates air is not free to all in the sense of cost-
ing nothing, for the coming of fresh air into the house means
an accompaniment of cold which must be counteracted by the
consumption of fuel. A mistaken idea of economy leads house-
holders, school boards, and college trustees to limit the size of
the air-ducts as well as of the rooms. It is therefore necessary
to emphasize the facts which science has fully established, in
order to secure the survival of the fittest of the race under the
present pressure of economic conditions, which take so little
account of the highest welfare of the human machine.

Air, water, and soil are the common possessions of man-
kind. It is impossible for man to use either selfishly without
injury to his neighbor and without squandering his inheritance.
Primitive man could leave a given spot when the soil became
offensive, and neighbors were then too few to require con-
sideration; but neither man nor beast could with impunity foul
the stream for his neighbor who had rights below him. The
soil is permanent; one knows where to look for it and its pollu-
tion. Air is abundant and is kept in constant motion by forces
of nature beyond human control, so that, save in the neighbor-
hood of an exceptionally offensive factory, man does not often
foul the free air of heaven ; it is only when he confines it within
unwonted bounds that it becomes a menace.

Water is the next precious commodity of the three. With-
out it man dies in a few days; without it the soil is barren;
without it air in motion parches all vegetation and carries
clouds of dust particles; without it there is no Hfe. As popu-
lation increases it becomes necessary to collect as much of the
rainfall as possible, to store it until needed, and to use it with
discretion. After use it is often loaded with impurities and sent
to deal death and destruction to those who require it later, and
yet, in nature's plan, it is the carrier of the world, and rightly
treated and carefully husbanded there is enough for the needs of
all. Its presence or absence has been the controlling force in
determining the habitations of men. In its ofl&ce of carrier it
not only brings nourishment in solution to the tissues of the

4 AIR, WATER, AND FOOD

human body, but also carries away the refuse material. It is a
cardinal principle in all sanitary reforms to get rid of that which
is useless as soon as possible. Too little water allows accumu-
lation of waste material and a clogging of the bodily drainage
system.

The average quantity needed daily by the human body is
about three quarts. Of this a greater or less proportion is taken
in food, so that at times only from a pint to a quart need be
taken in the form of water as such.

Next in importance to quantity is the quality, dependent
somewhat upon the uses to which it is to be put. As a rule,
the moderately soft waters are the best for any purpose. For
drinking purposes water must be free from dangers to health in
the way of poisonous metals, decomposing matters, and disease-
germs. For domestic use economy requires that it should not
decompose too much soap. Manufacturing interests require
that it should not give too much scale to boilers; for agriculture
there should not be too much alkali.

From the nature of things, no one family or city can have
sole control of a given body of water. Those on the highlands
may have the first use of the water, which then percolates to a
lower level and is used by the people on the slopes over and
over before it reaches the sea to start again on its cycle of vapor,
cloud and rain, brook and river. Although receiving impurities
each time, there are many beneficent influences at work to
overcome the evils resulting from this repeated use. That
which is dissolved from one portion of earth may be deposited
on another. As the plant is the scavenger of the air, withdraw-
ing the carbon dioxide with which it would otherwise become
loaded, so the water has also its plant hfe, purifying it and
withdrawing that which would otherwise soon render it unfit
for any use.

Pure water is found only in the chemical laboratory; the most
that can be hoped for is that human beings may secure for them-
selves water which is safe to drink, which will not impair the
efficiency of the human machine.

THREE ESSENTIALS OF HUMAN EXISTENCE 5

The importance of the third essential for human life, food,
and the close interdependence of all three, may be clearly shown.
Of little use is it to provide pure air and clean water if the sub-
stances eaten are not capable of combining with the oxygen of
the air or of being dissolved in the water or the digestive juices;
of less use still is it to partake of substances which act as irri-
tants and poisons on the tissues which they should nourish, and
thus prevent healthful metabolism and respiratory exchange.

And yet a large majority of those who have acquired some
notion of the meaning and importance of pure air and are be-
ginning to consider it worth while to strive for clean water pay
not the least attention to the sanitary qualities of food; the
palatable and aesthetic aspects only appeal to them.

Steam-power is produced by the combustion of coal or oil.
Human force is derived by releasing the stored energy of the
food in the body. The delicately balanced mechanism of the
human body suffers even more from friction than the most
sensitive machine, and the greatest loss of potential human
energy occurs through ignorance, carelessness, and reckless dis-
regard of nature's laws in regard to food.

It is necessary to know, first, what is the normal compo-
sition of a given food-material. This is found by analyses of
many typical samples. Second, is the sample under consider-
ation normal? To answer this requires an analysis of it, and a
comparison of the results with standards. If it is not normal,
in what way does it depart from the standard both in health-
fulness and in quality? Third, if a food-substance is normal,
what are its valuable ingredients and in what proportions are
they to be used in the daily diet?

In regard to meat, milk, and fish, the sanitary aspect for the
chemist resolves itself into two questions: Is the substance so
changed as to become a possible source of poisonous products?
Or has anything in the nature of a preservative been added to
it? If so, is it of a nature injurious to man?

There is, however, a great range of quality in some of the
most abundant foodstuft's, such as the cereals, especially in the

AIR, WATER, AND FOOD

nitrogen content. This is most important to the vegetarian
and to institutions where economy must be practiced. The fol-
lowing variations in the composition of leading cereals will
illustrate:

Water.

Nitro-
genous
substance.

Crude
fat.

Carbo-
hydrates.

Fibre.

Ash.

Oats, maximum

Oats, minimum

Oats, American hulled

Corn, maximum

Corn, minimum

20.80
6. 21

22. 20
4.68

18.84

6.00

13-57

14-31

5-55

10.65
2. II
7.68
8.87
1-73

.63

20.

.69

•37

I .

.08

■75

.08

■45

■30

■99

8.64

1-34
2.03

3-93
0.82

One sample of wheat flour may contain 14 per cent of nitro-
genous substance, another may yield only 9. A day's ration,
500 grams, will give 70 grams of gluten, etc., in the one case
and only 45 in the other. This difference of 25 grams would be
a serious factor in the dietary of an institution where little ad-
ditional protein is given, and it alone might be the cause of
dangerous under-nutrition.

The next step would naturally be to determine how definitely
these varying percentages mean varying nutrition. To this end
a study of vegetable nitrogenous products in their combination
or contact with cellulose, starch, and mineral matter is needed.
Much work remains to be done before these questions can be
even approximately answered.

At the low cost of one cent a pound, common vegetables
yield only about one-fifth as much nutriment as one cent's
worth of flour, yet they contain essential elements and deserve
to be carefully studied.

The sanitary aspect of food demands a study of normal food
and food value even more than of adulterants or of poisonous
food, ptomaines and toxines. The cultivation of intelligent
public opinion is most important, and each student should go
out from a sanitary laboratory a missionary to his fellow men.
That is, the office of a laboratory of sanitary chemistry should
be so to diffuse knowledge as to make it impossible for educated

THREE ESSENTIALS OF HUMAN EXISTENCE ^

people to be deluded by the representations of unprincipled
dealers. Freedom from superstition is just as important in
this as in the domain of astronomy or physics. So long as
chemists are employed by manufacturing concerns in making
adulterated and fraudulent foodstuffs, so long must other
chemists be employed in protecting the people until the public
in general becomes wiser. A part of the common knowledge of
the race should be the essentials of healthful living, in order that
the full measure of human progress may be enjoyed.

There is needed a greater respect for food and its functions
in the human body, a better knowledge of its effect on the
daily output of energy, its absolute relations to health and life,
and the enjoyment of the same. The familiarity with these
facts which is given by a few hours' work in the laboratory will
make a lasting impression and will enable the student to benefit
his whole life, even if he never uses it professionally. It is
purely scientific knowledge, just as much as that derived from a
study of the phases of the moon or the formulas of integration.

The variety of operations in such work, calling for great
diversity of apparatus and methods, is an educational factor
not to be overlooked in laboratory training.

For all detailed discussions and methods the reader is re-
ferred to such works as those of Wiley, Allen, Leach, etc., but
for the student who needs to study, as a part of general educa-
tion, only typical substances, and such methods as can be
carried out within the limits of laboratory exercises in a col-
lege curriculum, the following pages are written. Not enough
is given to frighten or discourage the student, but enough, it
is hoped, to arouse an interest which will impel him at every
subsequent opportunity to seek for more and wider knowledge.

Food is too generally regarded as a private, individual matter
rather than as a branch of social economy; it is, however, too
fundamental to the welfare of the race to be neglected. Society,
in order to protect itself, must take cognizance of the questions
relative to food and nutrition.

Formerly each race adapted itself to its environment and

8 AIR, WATER, AND FOOD

trained its digestion in accordance with the available food
supply. In America to-day the question is not how to get
food enough, but how to choose from the bewildering variety
offered that which shall best promote the health and develop
the powers of the human being, and, what is of equal impor-
tance, how to avoid over-indulgence, which weakens the moral
fibre and lessens mental and physical efficiency. In spite of all
preaching, few really beHeve that plain living goes with high
thinking. Professor Patten says that the ideal of health is to
obtain complete nutrition. Over-nutrition as well as under-
nutrition weakens the body and subjects it to evils that make
it incapable of survival.

No other form of social service will give so full a return for
effort expended as the help given toward better diet for children
and students. Fortunately help is coming fast. The United
States Government is giving much study to food problems, and
by publications is making available the work of other countries.
The later bulletins Hsted in the bibliography at the end of this
volume are especially valuable. What is now needed is a gen-
eral recognition of the importance of the subject.

CHAPTER II

AIR AND HEALTH

The air we breathe is a mixture of various gaseous substances
containing more or less finely divided solid particles. What
may be called "pure" air contains 20.938 per cent * by volume
of oxygen, 0.031 per cent of carbon dioxide, 78.09 per cent of
nitrogen, 0.94 per cent of argon and other rare gases belonging
to the argon group.

All the air with which we actually have to deal contains also
varying amounts of moisture, expressed in terms of "relative
humidity." Air at a low temperature can hold much less
moisture than at a high temperature. For example, one cubic
foot of air at 20° F. will hold 1.235 grains of water vapor, while
at 70° 7.98 grains will be held. The relative humidity is the
ratio of the amount of moisture which the air actually contains
to the amount which it could hold at the same temperature if
completely saturated. As water vapor is lighter than dry air,
the higher the humidity the less will a given volume of air
weigh. This effect is familiar in the action of a barometer
which falls on the approach of a rain storm, — the reading
on such an instrument being dependent on the weight of air
above it.

Besides moisture, the air in cities may contain a variety of
substances such as ammonia, sulphur dioxide, sulphur trioxide,
etc., and almost always dust, bacteria, yeasts, and molds.
Samples of air f taken in the down town districts of New York
and Boston showed at the street level numbers of dust particles
per cubic foot of air varying from 170,000 to 500,000, the num-

* Benedict, Composition of the Atmosphere. Carnegie Institution, Publication
No. 166.

t G. C. Whipple and M. C. Whipple, Am. J. Pub. Health, 1913, 3, p. 1140.

lO AIR, WATER, AND FOOD

ber gradually decreasing as the height above the street increased,
until only about 27,000 were found in the air taken from the
fifty-seventh floor of the Wool worth Building, 716 feet high. In
a house, school room or public building the numbers of dust
particles are equally variable, wuth a tendency to be somewhat
higher, depending on the location of the building, and whether
or not the air entering is purified. Thus in an investigation of
the air of school rooms,* few cases were found where the num-
bers were less than 200,000 per cubic foot, and they varied from
this to over 1,500,000, the greater proportion being between
200,000 and 600,000, much higher than is generally found in
outdoor air. The numbers of bacteria found in the air are small
compared to the dust particles, there being about 200" ^^ many
in outdoor air, and even less in indoor air, in 85 per cent of the
samples taken in school rooms f the number of micro-organisms
being less than 150 per cubic foot. In country districts the
numbers of both dust particles and bacteria in the air are ex-
tremely small.

Under ordinary conditions the presence of dust and bacteria
has no particular significance. In fact it is the opinion of most
sanitarians that the danger of the spread of disease by the
carrying of bacteria through the air is small, the contact neces-
sary for this to happen being much closer than generally exists
in oflices and schoolrooms. There are certain special cases
where dust particles may be harmful, — such as the dust con-
sisting of small particles of metal found in certain factories,
and the organic dust found in the air in certain rooms in textile
mills. Some of these dusts, such as white lead, are themselves
actually poisonous to the system, while others lodge in the
lungs and lower the vitahty so that pneumonia and tuberculosis
are more liable to gain a footing.

Poisonous gases are occasionally found in air, — the most
important being carbon monoxide which comes from leaky gas
jets or pipes, or from a defective furnace. As this gas has al-

* Winslow, Am. J. Pub. Heallh, 1913, 3, p. 1158.
t Winslow, loc. cil.

AIR AND HEALTH II

most no odor, insensibility may occur without the victim realiz-
ing what is taking place. For this reason it has been found
necessary, where this gas is used for lighting, to require the in-
troduction into it of some substances with strong odors. Car-
bon monoxide acts as a poison by combining with the hsemo-
globin of the blood, and preventing the absorption of oxygen.

In the air of mines, methane, — or fire damp as it is called, —
is sometimes present. This forms an explosive mixture with
oxygen, and is frequently the cause of mine explosions.

Respiration. — External respiration consists of alternately
filling and emptying the lungs. In the lungs, oxygen, breathed
in with the air, is exchanged for carbon dioxide brought to the
lungs by the blood. The blood leaving the lungs contains oxy-
gen which is carried to all parts of the body, and passes * from
the blood in the capillaries into the tissues where oxidation takes
place. The carbon dioxide formed passes back into the blood
and hence into the lungs. Expired air, therefore, contains less
oxygen and more carbon dioxide than inspired air. An average
composition would be, — oxygen, 16.03 P^r cent; carbon di-
oxide, 4.38 per cent; nitrogen, etc., 79 per cent.

The process of exchange of oxygen and carbon dioxide in the
lungs is partly a physical one, — that is, the vapor pressure of
oxygen is greater in the lungs than in the blood, and, therefore,
oxygen passes from the former to the latter. With carbon
dioxide the reverse is true. Therefore, if air high in carbon
dioxide is breathed into the lungs this will increase the vapor-
pressure of this substance, and hinder the elimination of it from
the blood. But it appears to be impossible to account for the
interchange of gases on a purely physical basis, and, therefore,
it is thought that enzymes, which aid in the interchange, are at
work.

Comfort. — The first two theories that were advanced to

account for effects of discomfort when a room becomes "close"

were based on the supposition that the products of respiration

were poisonous when taken back into the lungs. In one theory

* See Haramarsten-Mandel. "A Text-book of Physiological Cheinistr>-."

12 AIR, WATER, AND FOOD

this poisonous substance was supposed to be carbon dioxide.
That animals cannot live in an atmosphere composed of nitro-
gen and carbon dioxide, and that oxygen is necessary has long
been known, but it was thought that carbon dioxide had a
specific poisonous action and, therefore, should be present in any
air used for human beings, in only very small amounts. This
theory has been entirely disproved and carbon dioxide can no
longer be regarded as in itself poisonous. If too much of the
oxygen in the air becomes displaced by carbon dioxide it is im-
possible for animals to utilize the oxygen left, but this only
happens when the oxygen content decreases to about 12 per
cent. Practically such a low per cent is never found, as inter-
change of the air between a room and the outside is continually
going on around windows and through walls. If, however, the
•oxygen is allowed to remain at about 21 per cent, very large
quantities of carbon dioxide may be present without any ill
effects. Experiments have shown conclusively * that carbon
dioxide cannot be blamed for discomfort in a crowded hall or
theatre.

The other theory, — known as the "crowd poison" theory
was based on some experiments which seemed to show that
organic poisons were given off during respiration, and that these
substances were the cause of the headaches and nausea some-
times experienced by sensitive persons in "close" rooms. At
the present time there are some adherents to this theory, but
there has been little real evidence produced in its support. The
first proofs of the non-poisonous character of exhalations were
obtained by Formanek in a long series of experiments f and
more recently Winslow J using the principles of anaphylaxis
failed to obtain any results which showed the presence of the
poisons (or toxins) in expired air.

At the present time it is quite generally believed that sen-

* See Crowder. "Ventilation of Sleeping Cars." Arch. Intern. Med., 1911, 7,

PP- 85-133-

t Archiv fiir Hygiene, 1900, 38, p. i.
I Loc. cit.

AIR AND HEALTH

sations of comfort and discomfort are dependent upon the rate
of loss of heat from the body. If this is normal, then comfort
results, if either too high or too low, then discomfort, headaches
and nausea may follow. Just what this heat loss should be,
measured in any system of units, is not known, but certain of
the methods by which the loss takes place, and the factors
which influence the rate may be discussed.

There are three ways by which heat can be transferred from
the body to the surrounding atmosphere, (i) Evaporation. —
The change from the liquid to the gaseous state is accompanied
by an absorption of heat. Thus when water evaporates from
the surface of the body, heat is removed with it. (2) Trans-
mission (by conduction and convection). Heat passes from a
warm to a cold body when the two are in contact. For the
greater part of the year the animal body is warmer than the
atmosphere, and, therefore, the latter is continually receiving
heat from the body. Since warm air rises, convection currents
may be set up carrying away the heat already given up to the
air. (3) Radiation. — The first two methods depend directly
on the presence of matter. In radiation heat is transferred in
all directions by means of ether waves, and the medium through
which the radiation takes place does not necessarily become
heated. There is no data available on the loss of heat from the
body in this way, and we do not know what part it actually
plays in comfort.

These three methods by which heat may be given off from
the body may be acting simultaneously, — in fact they generally
are doing so, — and one or more may be negative in its action, —
that is may be supplying heat to the body. Further, while they
act entirely independently of each other, they are each in-
fluenced by the same conditions of the atmosphere, and it is
these physical conditions which are the ones capable of regu-
lation, and which determine good or bad ventilation. These
are, — temperature, humidit}' and motion.

Temperature. — Temperature affects evaporation, because the
higher the temperature of the air the more moisture is it cajxible

14 AIR, WATER, AND FOOD

of taking up. It affects conduction, because the greater
the difiference of temperature between two bodies the greater the
amount of heat passing from that at the higher to that at the
lower temperature. It affects convection, because convection
currents are started by warm air rising and cooler air taking its
place.

Humidity. — Heat loss by evaporation is more dependent on
humidity than on any other factor. Relative humidity is a
measure of the per cent saturation of the air by water vapor,
and it is obvious that the higher the humidity the less will be
the opportunity for the air to take up more moisture, and,
therefore, the less rapid the evaporation from the body. Trans-
mission of heat from the body is affected by the humidity, be-
cause moist air is a better conductor than dry air, and, therefore,
the higher the humidity the greater the rate of heat conduction.
(Relative humidity, as can be seen from a foregoing discussion,
is itself affected by the temperature.)

Motion. — The motion of the air influences evaporation by
carrying away from the body more or less rapidly the air which
has become completely saturated with moisture, and thus al-
lowing access to unsaturated air. If the air and the body are
perfectly quiet evaporation will be gradually retarded until it
is nearly zero. Convection currents are movements in the air
started by differences in temperature. These movements will
be greatly increased by any motion in the air, and, therefore,
the greater the motion the more rapid will be the transference
of heat in this way.

It is important to remember that these three factors, tem-
perature, humidity and motion, — are always acting simul-
taneously, and that there may be an increase in the rate of heat
loss above the normal by one or more of them at the same time
that the rest tend to decrease this rate. Furthermore, the same
factor, humidity for example, may tend to increase the heat loss
above the normal by one method, — perhaps by evaporation, —
while at the same time, the same degree of humidity may tend
to decrease below the normal the heat loss by another method,

AIR AND HEALTH 1 5

perhaps by transmission. The degree of comfort felt under any
specified conditions is, therefore, the resultant of all effects, some
tending to increase and others to decrease the rate of heat loss
from the normal.

This can be readily illustrated. Suppose that the temper-
ature is 95° F., the humidity 90 per cent and there is but very
little motion in the air. The result is well known, — a feeling
of heaviness and considerable discomfort. Why?

(i) The high temperature allows the air to take up a con-
siderable amount of moisture, thus tending to increase the heat
loss by evaporation, with the consequent cooling effect on the
body. On the other hand, the heat loss by conduction, con-
vection and radiation arc only very small as they depend on
the difference of temperature of the body and the air.

(2) The high humidity prevents the rapid evaporation of
moisture, and, therefore, tends to decrease the heat loss from the
body. This more than counteracts the increased capacity of
the air for moisture, due to the high temperature. On the
other hand, the high humidity makes the air a better conductor
of heat, and, therefore, tends to increase the heat loss by con-
duction. This, again, is counteracted by the high temperature,
temperature being the more important factor in this method of
loss.

(3) The very slight motion of the air tends to decrease the
heat loss by evaporation and convection.

The net result is that heat does not leave the body as rapidly
as it should, and we feel hot and uncomfortable.

Application of this theory of regulation of loss of heat is not
wholly adequate to explain all conditions. Another factor seems
to be involved, that of loss of moisture, apart from any loss of
heat which accompanies this. "Probably much of the harm
attributed to damp and to cold is due to diminished water cir-
culation, etc."* With this added factor it is possible to ex-
plain most of the uncomfortable conditions. The uncertainty
of the theory lies in the fact that we have been unable to test it

* Macfie, Air and Health.

AIR, WATER, AND FOOD

THE CURVE OF COMFORT

R«

ilati

TO I

lun

idit

|40

[=.50

<>.

i^€^^'

r ,

Srn

pp-

^^'

«-?

P.
S

^,u

>■

-t'

o<>^

inn

Mean annual temperature and humidity of health resorts:

1 Algiers 5

2 Alexandria 6

3 Cairo 7

4 Bermuda 8

Unfavorable to white man's residence:

9 New Orleans 12

10 , Havana 13

Arequipa
Luxor-winter
Los Angeles
Madeira

Persia
India

II Malay Archipelago 14 Singapore
A-B Most comfortable for indoor workers (Hill).

AIR AND HEALTH 17

experimentally and to determine the exact heat loss due to each
factor.

Hill * has plotted a series of curves which are intended to
represent the various conditions of comfort in terms of tem-
perature and humidity. Thus it is seen that a temperature of
55° F. and a humidity of 70 per cent gives comfort, and as the
temperature increases the humidity must be decreased. At
68° F., the temperature generally desired in the house, the
humidity must be around 50 per cent.

Ventilation. — In ventilating a public building or a house, it
is necessary to supply a sufficient quantity of air in the proper
condition. In most cases this condition is, that the air in the
room shall be at a temperature of 68° to 70° F., and with a
humidity of 50 to 70 per cent. As long as the humidity does
not go too high, it seems to be a secondary factor so far as health
is concerned. More discomfort is felt from overheating than
from any other cause. This is also true in many factories, but
there are some where high humidity must be considered, such
as is necessary to maintain in connection with certain textile
operations. It should be remembered that the higher the tem-
perature the more sensitive does one become to high himiidity.

Another condition which must be met in ventilation practice
is that governed by the carbon dioxide content of the air. As
pointed out above, this substance is not itself poisonous, but it
is useful in serving as an index of the amount of unused air be-
ing supplied. The normal individual gives off from 0.6 to 0.8
cubic feet of carbon dioxide per hour, and this will gradually
accumulate in a room unless the air is continually being replaced.
The amount of carbon dioxide present in a room can, therefore,
be used to determine whether or not there is sufficient replace-
ment of used air by fresh air. The allowable amount of carbon
dioxide is about 10 parts per 10,000 of air. Arnounts above this
may be allowed in certain special cases where the carbon dioxide
does not come from man or animals. If only 6 or 7 parts are
present, the ventilation may be considered excellent. In order

* Hill, Recent Advances in Physiology and Biochemistrj'.

l8 AIR, WATER, AND FOOD

to accomplish this about 2000 cubic feet of fresh air per person
per hour must be supplied. The amounts actually recommended
depend somewhat on the use to which the room or building is
to be put, these amounts varying between 1000 cu. ft. for a
waiting room and 2500 for a hospital. Where it is difficult to
determine how many people will be present the calculations may
be based on the number of complete changes of air per hoar,
these being from one to five in a residence, and from one to two
in an auditorium.*

It is also possible to calculate from analytical data the inter-
change of air going on under given conditions, and thus test the
efficiency of a ventilating system. If, after a room has been
occupied and the occupants removed, the air is analyzed for
carbon dioxide, the room allowed to remain a definite length of
time, and another analysis made, the interchange may be cal-
culated from a formula given by Barker: f

^=f'°^(l^:)

where C is the contents of the room in cubic feet, T the time in
hours between the original amount of carbon dioxide ki in one
cubic foot of air, and the final amount ^2 in one cubic foot of
air, a the proportion of carbon dioxide in one cubic foot of pure
atmospheric air, and V the interchange in cubic feet per hour.

Ventilation depends on the movement of air currents in such
a way as to continually supply fresh air and to remove used
air. This must be done so that no drafts will be felt at any
part of the room. The system actually used will depend on
the kind of building and room, — as well as on the kind of heat-
ing used. In the ordinary dwelling house ventilation is almost
ahvays left to look after itself. Even in the best built houses
there is going on constantly an interchange of air around the
windows and doors. This is not sufficient on winter evenings

* Greene, "Elements of Heating and Ventilation," p. 23.

t Baker, "The Theory and Practice of Heating and Ventilation," p. 164. A
number of other useful ventilating formula; are also given.

AIR AND HEALTH 19

when kerosene or gas lamps are burning, and most rooms soon
become stuffy. To aid this natural ventilation, windows, open
fire places and hot air furnaces are used. Excellent results may
be obtained from the careful use of the open window, but it re-
quires considerable time as well as care to operate them so that
no drafts will result. Where a hot air system of heating is used
a house may be well ventilated, — the air which is forced in
through registers going out after proper circulation, through ven-
tilators or around windows. Care should be taken to place
registers to get this circulation.

In a large building, — office, educational, or auditorium, — the
problem is somewhat different. Here it is useless to depend on
natural ventilation and some artificial means must be employed.
There are two general methods of air circulation in use, upward
and downward. Both have their advantages and disadvantages.
Upward ventilation would seem theoretically the best, as ex-
pired air, being warm, rises and creates an upward current,
which can be easily drawn into an outlet. This system can be
used, but it presents certain difficulties. The first is that un-
less air comes into the room through a very large number of
small holes in the floor, drafts of cold air around the feet are
certain to be felt. This would only be practical in an audi-
torium with stationary seats. Besides, objection is sometimes
made that odors from the clothing are made more noticeable by
being carried past the nose. The reverse system, downward ven-
tilation, seems to be more practical. Here the air is introduced
from the ceiling and is drawn out through ducts in or near the
floor. More often air is introduced from the walls of the room.
In this case it is necessary to so arrange the inlet and outlet
that air from the former will circulate around the room before
reaching the latter. To do this, the outlet is generally placed
a little below the inlet on the same wall, this being on the cold
side of the room. The air may be forced into the room under
pressure from a fan, called the plenum system, or may be drawn
out from the room by a fan in the outlet, called the vacuum
system.

20 AIR, WATER, AND FOOD

In cities where there is necessarily much smoke and dirt,
it may be considered best to purify, in some way, the air
entering a building. The simplest method is to screen the in-
coming air through fine wire gauze or cheese cloth. A more
effective way is by means of air washers. All of these, and
there are a number of them on the market, depend on the pas-
sage of the air through a spray of water which removes dirt,
bacteria and soluble substances. Since these machines spray
water into the air they are also humidifiers, and may be used as
such, particularly in textile factories where it is necessary to
carry on certain operations in moist air.

It is also possible to take air out of a room, wash it, cool it
and send it back into the same room.* This would effect a
saving of coal if it w^ere practical to operate.

Another method which has been in some use for purifying air
is by means of ozone. During the last year there has been much
discussion on this subject, f and very serious doubts have been
thrown on the real usefulness of this method. That ozone in
the presence of a large amount of moisture is a good disinfectant
cannot be denied, but under the dry conditions of the atmos-
phere its germicidal efi'ect is small. However, in most cases it
is not bacteria which we need to kill, but odors. On this point
the evidence is not quite so clear. Most are agreed that the
odors disappear, but it is still a question whether the substances
producing them are actually destroyed, or whether the odors
are masked by those of ozone. From a standpoint of health,
this would also be immaterial if it could be proved that the
ozone itself was harmless to breathe. At the present time the
evidence seems to be the other way.

* See article on Recirculated Air. McCurdy, Am. Phys. Ed. Rev., Dec, 1913.
t Jordan and Carlson, J. Am. Med. Assn., 1913, 61, pp. 1007-1012; Norton,
Eng. Rec, 1913, 68, p. 732; Vosmaer, /. Ind. E)ig. Chcm., 1914, 6, p. 229.

CHAPTER III
air: analytical methods

In an investigation of the air of any room or public building
it is not enough to make one or two observations, as these might
be entirely misleading, but a sufficient number must be taken
to get a fair estimate of the conditions. Thus in a room, read-
ings of the physical instruments must be made and samples
for chemical analysis taken at a number of points, and these
repeated at intervals of five or lo minutes until six or eight have
been taken. Slight changes constantly occur which are not of
any importance in practical work, but fortunately most of the
instruments and most of the methods used are not delicate
enough to be influenced by changes of this character. In short,
it is average conditions which are of importance, and which
should be recorded.

Physical Determinations. — Temperature. — The use of the
thermometer is too well known to need any detailed statement.
Mercurial thermometers are the most accurate for practical
work, but care should be taken that the bulb of the thermome-
ter is suspended in the air and not placed against a wooden
back, as in the latter case the reading lags behind the actual
changes in the temperature of the air. Where it is desired to
have a continuous record, recording thermometers are to be
recommended. These depend on the contraction and expan-
sion of a metal combination, with the changes of temperature,
the metal being connected with a pen which records the changes
on a paper disc moved by clockwork.

Pressure. — Air pressure is measured by barometers, of which
there are two types, — mercurial and anaeroid, both of which
are well known. Since the barometric reading depends on the
weight of the column of air above the instrument, the reading

22 AIR, WATER, AND FOOD

will vary with the distance above sea level, and with the com-
position of the air. In the latter case the only important factor
is moisture. As water vapor is lighter than dry air, the larger
the moisture content the lighter the moist air and the less the
pressure. Thus a low barometric reading indicates the ap-
proach of a storm.

Humidity. — Relative humidity has already been described.
The most accurate method of measurement is by means of wet
and dry bulb thermometers. The rate of evaporation of water
into air at any one temperature depends on the amount of
moisture already present. Since evaporation is accompanied by
absorption of heat, the surface from which the water evaporates
will be cooled in proportion to the rate of evaporation. If the
bulb of a thermometer is surrounded by a film of moisture,
which can readily be done by means of a piece of cloth or wick
with one end dipped in a reservoir of water, this cooling can be
measured by the lowering of the temperature below that of a
thermometer whose bulb is surrounded by air alone, and the
lowering is proportional to the relative humidity. In the ap-
pendix will be found a table from which the relative humidity
can be obtained from the reading of the dry and wet bulb ther-
mometers. In order that the wet bulb thermometer may come
quickly to equilibrium an instrument called the psychrometer
has been devised for rapidly rotating the thermometers.

Another method of measuring the humidity is by means of
the hair hygrometer. In this instrument a number of horse
hairs arc placed under tension by means of a small weight.
The distance to which the hairs will be stretched will depend on
the amount of moisture taken up from the air, — the higher
the moisture the greater the stretching. The weight can be
readily connected to an indicator which will record the rela-
tive humidity on a dial, or a pen can be attached, to make a
recording instrument, in a similar manner to that used with a
recording thermometer.

Motion. — Where the velocity of air is considerable, as in the
case of wind or in such places as ventilation ducts, measure-

AIR: ANALYTICAL METHODS

merits can be made by the use of anemometers. However, in a
room, the movement of air is much too slow, and the direction
of currents too varied, for such an instrument to be of use.
The best method is by use of smoke from a joss stick or cigar.*

Dust. — The simplest method for determining dust in air is to
draw a measured quantity of air through a weighed tube con-
taining a cotton plug. For this it is necessary to have a suction
pump, — the variety which may be attached to a water faucet
is useful, — a meter, such as a gas meter, and a tube containing
a cotton plug. The tube with the plug should be dried in a
desiccator before each weighing as moisture may be absorbed
from the air passed through. Knowing the amount of air and
the increase of weight of the cotton filter, the amount of dust
per unit volume of air can be calculated. Where the amount of
dust is large, the cotton plug can be replaced by one of granulated
sugar. The amount of dust is then determined by dissolving
the sugar in water and then filtering through a weighed Gooch
crucible.

The most accurate determinations of dust particles can be
made by m^eans of the "Dust Counter" or the "Koniscope."
Both of these instruments f are too expensive to be very generally
used.

An apparatus for taking dust samples of air has recently been
described by Baskerville,| and would seem to be useful and
sufficiently accurate for practical purposes.

Chemical Determinations. — The first systematic study of
the atmosphere was made by Scheele, in 1779, shortly after the
discovery of oxygen. Since that time more and more accurate
methods have gradually been developed, culminating in that
used recently by Benedict. §

* Shaw, " Air Currents and the Laws of Ventihition." Cambridge. 1907.

t See "Standard Methods for the Bacterial Examination of Air," Am. Pub.
Health Assn., 1910, p. 38.

X J. hid. Eng. Cliem., 1914, 6, p. 238.

§ For a detailed history of air analysis see Benedict, "The Composition of the
Atmosphere with Special Reference to its Oxygen Content," Carnegie Institution
of Washington, 191 2, Publication No. 166.

24 AIR. WATER, AND FOOD

In practice the only chemical test made on air is that for
carbon dioxide. In cases of poisoning, tests may be made for
carbon monoxide or methane, and in experiments with respira-
tion, oxygen determinations together with those for carbon
dioxide are considered necessary.

The methods for the determination of carbon dioxide are all
based on absorption by alkalies, the amount of this absorption
being measured either by direct determination of the diminution
of a given volume of air, or by determination of the amount of
alkali used for the absorption.

Collection of Samples. — ■ Methods for collecting samples of air
for chemical analysis will vary somewhat with the method and
apparatus used. In certain cases the sample is measured
directly into the analytical apparatus, while in others, — and
these are the more practical methods, — • the sample is first col-
lected in a balloon or bottle. Where large amounts are needed,
as in the Pettenkofer method, the samples are collected in a
four- or six-liter bottle, the volume of which has been determined
by weighing both empty and filled with water. The bottle is
fitted with a two-hole rubber stopper with a short piece of glass
tubing to serve as an inlet in one hole and a long brass tube ex-
tending to the bottom of the bottle, in the other hole. This
brass tube is connected to a bellows with the valves arranged so
that air will be drawn out of the bottle. Pumping should be
continued until the air originally in the bottle has been entirely
replaced, which will take from 30 to 50 strokes of the bellows.
The stopper and tube are then removed, and the bottle closed
with a stopper as described on page 34.

For the Walker and the Cohen and Appleyard methods a
much smaller volume is all that is needed, — from 500 c.c. to
two liters. The simplest method is to fill the bottle with water
and pour it out. This has the disadvantage that expired air
from the collector may reach the bottle.

A better method is to fit two bottles each with a 2-hole
rubber stopper. In one hole of the stopper of bottle (A) (Fig. i)
insert a short piece of glass tubing, and in the other a longer

AIR: ANALYTICAL METHODS

piece of tubing extending nearly to the bottom of the bottle.
In the stopper of {B) insert a short piece of glass tubing just
reaching through the stopper, and a longer tube extending
nearly to the bottom, and
fitted with a piece of small
bore rubber tubing and a
pinch clamp. Connect the
short tube of bottle {B) with
the long tube of (^4) by means
of a rubber tube and close
with a pinch clamp. Fill {B)
with recently boiled water,
open clamp (a), close clamp
{h) and insert stopper with
connections, into the bottle.
Then close {a). Invert {B)
at the point at which the sam-
ple is to be taken. Release
the pinch clamp (a), and then
open the clamp {b). The bot- .
tie filled with air (B) is then
closed with a solid rubber
stopper and is ready for
analysis. If bottle {A) is
larger than {B) it can be
used, together with the water, for taking a number of samples
of air.

Another method by which sampling is made easier, but which
does not give such accurate results, is the steam vacuum method.
The apparatus is set up as in Fig. 2. Steam is supplied from a
two-quart oil can nearly filled with water, or if preferred, from a
liter flask. A rubber tube and piece of glass tubing connects
the steam can with the inverted bottle, the size of which de-
pends on the method of analysis used, the tube extending to
within an inch of the bottom of the bottle. The bottles are
made for ground glass stoppers, but are fitted with rubber

Fig. I.

AIR, WATER, AND FOOD

stoppers to which have been applied a thin coating of vaseline.
Too much vaseline should be avoided, as it prevents the stopper
staying in after the sample has been collected. The rubber
stoppers should be one size larger than would ordinarily be used.
To prepare the bottle, fill the can two-thirds full with water,
and boil for a few minutes to expel carbon dioxide and air. In-

FlG. 2.

vert the empty bottle over the end of the tube, and allow to
remain for three minutes. Keeping the bottle inverted, re-
move it from the tube, and quickly insert the rubber stopper.
The stopper may be pushed in more securely by holding it
against the table with a slight pressure, and keeping it there
until the vacuum starts to form. When cool, the stopper should

AIR: ANALYTICAL METHODS 27

project at least one-half an inch in order to be easily removed.
A number of bottles can be prepared in the laboratory, and quite
easily transported. All rubber stoppers which are used should
first be boiled in dilute caustic soda, then in a dilute solution of
potassium bichromate and sulphuric acid and thoroughly
rinsed.

To collect the sample it is necessary only to remove the stopper,
taking care to hold the bottle away from the face in order to
prevent contamination from the carbon dioxide of the breath.

At the time of collecting the samples the following observations
should be recorded: room, date, time, weather, place in room,
number of people present, number of gas jets or lamps burning,
number of doors, windows and transoms, methods of heating
and ventilation, and anything else which would tend to in-
fluence the amount of carbon dioxide present.

In collecting samples, care must be taken to avoid currents of
air or the close proximity of people. Exact duplicate analyses
can be obtained only in empty or in nearly empty rooms. Even
two sides of the same room will probably show differences, but
two samples taken carefully side by side ought to agree within
0.05 part per 10,000.

Carbon Dioxide. — The most accurate analyses of air have
been those obtained by Benedict by means of an apparatus
especially designed by Dr. Klas Sonden.* The analysis de-
pends upon the measurement of the decrease in volume of a
sample of air after contact with a caustic alkali solution. An-
other accurate apparatus on the same principle is that of Petter-
sen-Palmquist, f which has been modified by Rogers, | and
more recently by Anderson. § In all of these forms the manipu-
lation is rather delicate, the apparatus is bulky to transport,
and when obtained, the results are much more accurate than is
necessary for any practical work.

* A description of this will be found in Publication No. 166, Carnegie Insti-
tution of Washington, already referred to.

t For description see Rosenau, " Hygiene and Preventive Medicine."
X See catalogue of Eimer and Amend.
§ /. Am. Cliem. Soc, 1913, 35, p. 162.

28 AIR, WATER, AND FOOD

Walker Method. — The method to be most recommended for
practical analyses for carbon dioxide is that proposed by Walker.*
It has been carefully studied in this laboratory f and slightly
modified. The results are accurate to tenths of a part per 10,000.

Principle. — To a definite volume of air, usually one to two
liters, is added a measured amount of standard barium hydrox-
ide, care being taken to avoid contact of the solution with the
air. After the absorption of the carbon dioxide, the solution is
filtered under reduced pressure through asbestos and the clear
barium hydroxide received into a known excess of standard
hydrochloric acid. The absorption bottle is rinsed out with
water free from carbon dioxide. The excess of acid is then
determined by titration with barium hydroxide. It is essential
for the complete absorption of the carbon dioxide that the barium
hydroxide be largely in excess, so that not more than one-fifth
of it is neutralized; furthermore, the absorbing solution must be
shaken with the air for a considerable time.

Reagents and Apparatus. — The standard solutions used are
N/50 hydrochloric acid, and barium hydroxide, approximately
N/ioo, its exact strength relative to the acid being found daily by
titration. It will be found advantageous to use solutions of
this strength, somewhat more dilute than those recommended
by Walker, on account of the increased accuracy with air nearly
free from carbon dioxide. The decreased range of usefulness is
readily compensated by the employment of smaller samples of
the impure air.

The barium hydroxide is preserved with especial care. The
hard-glass bottle containing it, placed on a high shelf so that
the measuring apparatus can be filled directly by gravity, is
heavily coated on the inside with barium carbonate. The bottle
is closed by a rubber stopper with two holes, one of which car-
ries the siphon tube dipping to the bottom of the bottle and
supplying the measuring burette, while the other carries a fairly
large glass T. (Fig. 3).

* J. Chem. Soc, 1900, 77, p. mo.

t Woodman, /. Afn. Chem. Soc, 1903, 25, p. 150.

AIR: ANALYTICAL METHODS

Fig. 3.

From one-half the horizontal arm of this projects a glass tube
carrymg the device for protecting the solution. This device is
shown drawn on a somewhat larger scale in the same sketch.
The horizontal tube enters the T tube
far enough to support the apparatus.
Connection is made by a closely-fitting
rubber tube. The longer tube, reach-
ing nearly to the bottom of the test-
tube, carries a fairly good-sized cal-
cium-chloride tube which contains
soda-lime, enclosed in the usual man-
ner by plugs of cotton. The test-tube
contains five to 10 c.c. of dilute (about
N/50) caustic potash colored with phe-
nolphthalein, the whole serving to in-
dicate the efficiency of the soda-lime.
From the other end of the horizontal
arm of the T projects, in the same way, a long tube bent at
right angles fitting by a rubber stopper into the top of the
burette, thus making the whole a closed system, much after
the manner of Blochmann.* Any air entering the bottle when
the solution is drawn from the burette or when the burette
is filled again must have come through the protecting appa-
ratus. This will be found efficient if care is taken in the selec-
tion or preparation of the soda-lime.f

The burette used for the barium hydroxide is a glass-stop-
pered one, differing somewhat from the ordinary form. The
portion below the graduations is narrowed and bent at a right
angle. This horizontal part is fitted with an ordinary glass
stop cock. This gives no trouble when kept well vaselined.
The tip of the burette is kept covered with a little rubber cap
when not in use, to prevent clogging from the formation of
carbonate. The apparatus could easily be arranged with a

* Ann. Chem., (Liebig), 1887, 237, p. 39.

t Directions for preparing a good quality of soda-lime are given by Benedict
and Tower, 7. Am. CJicm. Soc, 1899, 21, p. 396.

3°

AIR, WATER, AND FOOD

special pipette for the delivery of a definite charge of a baryta
solution.

The apparatus used for filtering off the barium carbonate is
shown in Fig. 4. On the base of a ring stand is placed an ordi-
nary filter bottle of about 250 c.c. capacity closed by a rubber
stopper with one hole. The suction pump is connected with the

tube on the side of the bottle. A Gooch
filtering-funnel, the upper part of
which is cut off so that the remainder
above the constriction is about an
inch long, is put through the rubber
stopper. The tip projecting into the
bottle is bent so that the liquid shall
flow down the side and not spatter.
A rather close coil of stout platinum
wire placed above the narrow portion
serves as a support for an asbestos
filter. A two-cm. Gooch filter plate
serves as well as the platinum wire.
In the upper part of the tube is a
tightly-fitting rubber stopper, through
which passes a narrow glass tube
extending to within one-eighth inch
of the asbestos layer, and provided
above the stopper with a stop cock.
Connection is made with the short
tube of the inverted bottle by means
of a rubber tube about 4 inches in length.

The inverted bottle is a carefully calibrated one of about
one liter capacity, and is used for collecting the sample, the
method preferably being by water displacement as described
on page 25. Record the temperature and barometric pressure
at the time the sample is taken. After collecting the sample the
bottle is closed by a solid rubber stopper. For filtering, this is
replaced by a rubber stopper through which pass two glass
tubes. The longer tube reaches nearly to the bottom of the

Fig. 4.

AIR: ANALYTICAL METHODS 31

bottle, is bent as shown, and contains a glass stop cock. The
shorter tube ends internally just flush with the stopper, and out-
side is fitted with a stop cock and projects just far enough to
make connection with the rubber tubing. The glass stop cocks
may be replaced by rubber tubing and Mohr pinch clamps.

The filter is made of washed asbestos, free from acids, in the
manner usual for Gooch crucibles. The same filter will do for
a number of determinations. The asbestos layer should be
about one-eighth of an inch thick and should be washed with
distilled water.

Procedure. — Remove the stopper from the cahbrated bottle
containing the sample of air, and run in rapidly from the burette
about 25 c.c. of the barium hydroxide solution, the exact amount
being determined from the burette readings. Immediately re-
place the rubber stopper, place the bottle on its side and shake
at very frequent intervals for 20 minutes, giving a sort of rotat-
ing motion so that the solution will spread over the bottle, and
thus expose a large surface for absorption of the carbon dioxide.

While the absorption is going on prepare the filter (although
it is better to prepare this, and to standardize the barium hydrox-
ide before starting the determination) and also make about
100 c.c. of wash water for each determination. This latter is
done by adding to distilled water one c.c. of a 10 per cent
barium chloride solution and three drops of phcnolphthalein,
then titrating with the barium hydroxide to a faint permanent
pink. Keep in a stoppered flask until wanted.

Standardize the barium hydroxide against the hydrochloric
acid in the usual manner. Employ some wash water for
diluting in place of distilled water, which contains some carbon
dioxide.

Measure into the filter bottle from a burette about 13 c.c. (or
an amount slightly more than equivalent to the barium hydrox-
ide used) of N/50 hydrochloric acid, the exact amount being
obtained from the burette readings.

After the absorption is finished remove the rubber stopper
from the bottle, and wash the stopper with a Httle of the wash

32 AIR, WATER, AND FOOD

water, letting the washings run into the bottle. Insert the two-
hole rubber stopper with connections for filtering and invert as
shown in the figure.

Open the upper stop cock and turn on the pump. Now slowly
open the filter stop cock and control the flow of liquid entirely
with this cock. The barium carbonate remains on the asbestos,
and the clear baryta solution which passes through is at once
neutralized by the hydrochloric acid. When all the hquid has
passed through allow the pump to act for a few minutes until
the bottle is partially exhausted, then close the filter cock.

Pour some of the wash water into a small beaker, dip the end
of the longer tube into it, and by opening the stop cock allow
about 20 c.c. to flow into the bottle before closing it. Un-
clamp the bottle and shake thoroughly while held horizontally
and still attached to the filter. Clamp it in place again, turn on
the pump, and draw the wash water through the filter. Repeat
this twice. Generally at the third washing the wash water no
longer turns pink, showing that the barium hydroxide has been
completely removed. If the pink color persists wash again.

Remove the filter bottle and titrate in the bottle, for the ex-
cess of acid, with barium hydroxide. The end point is a distinct
pink which is permanent for one minute.

To obtain the amount of carbon dioxide subtract the number
of cubic centimeters of N/50 acid used from the number of cubic
centimeters of acid equivalent to the barium hydroxide used.
This will give the amount of carbon dioxide in the sample in
terms of N/50 acid, from which the actual number of grams of
carbon dioxide can be obtained. From the table in the ap-
pendix * obtain the weight of one cubic centimeter of carbon
dioxide for the conditions of temperature and pressure observed
when the sample was taken. From this the volume of carbon
dioxide in the sample can be calculated, and knowing the vol-
ume of the bottle, and making allowance for the 25 c.c. of alkali

* Dietrich's Table, the one in general use, is not absolutely correct, the weight
of a cubic centimeter of carbon dioxide at 0° C. and 760 mm. being somewhat
different from that given at present by the best authorities, but it is sufficiently
close for any but the most exacting work.

AIR: ANALYTICAL METHODS 33

added, the parts of carbon dioxide per 10,000 of air can be
calculated.

A sample calculation follows:

Standardization: — i c.c. Ba(0H)2 = 0.48 c.c. N/50 HCl.
Volume of bottle = 991 c.c. Temperature = 18° C. Ba-
rometer = 764 mm.
Total Ba(0H)2 used 58.02. HCl used = 26.08.
58.02 c.c. Ba(0H)2 = 58.02 X 0.48 = 27.85 c.c. HCl.
27.85 — 26.08 = 1.77 c.c. N/50 acid equivalent to the CO2

present.
Since i c.c. N/50 acid = 0.44 mg. CO2, then there are

present in the sample 0.78 mg. CO2.
I c.c. CO2 at 18'' and 764 mm. weighs 1.817 mg. .". 991 —
25 = 966 c.c. of air contains .429 c.c. CO2 or 4.4 pts. CO2
per 10,000.
If the amount of carbon dioxide present exceeds 25 parts per
10,000, either a 500 c.c. bottle may be used for collecting the
samples, or double the quantities of barium hydroxide and hydro-
chloric acid should be added. Such a condition rarely exists
in practical work.

Pettenkofer Method. — The method which for many years
was generally employed for the estimation of carbon dioxide in
the air of rooms is a modification of that originally devised by
Pettenkofer,* While this method is convenient, and for a long
time has been the favorite, it is now quite generally recognized
that it contains inherent sources of error which can be obviated
only by the use of complicated apparatus and extreme skill in
manipulation. It should, therefore, be borne in mind that the
results obtained are generally too high even though agreeing
closely among themselves.

Principle. — The principle is essentially the same as that of
the Walker method, i.e., the absorption of carbon dioxide from
a known volume of air in barium hydroxide solution and the
titration of the excess with standard sulphuric acid.

* Pettenkofer, Annalen, 2, Supp. Band, 1862, p. i; Gill, Aiulyst, 1892, 17,
p. 184.

34 AIR, WATER, AND FOOD

The samples are collected in four- or six-liter bottles, as de-
scribed on page 24, each provided with a rubber stopper carry-
ing a glass tube over which a rubber nipple or cap is slipped.
Note particularly the temperature and barometric pressure.

Reagents and Apparatus. — The solutions used are sulphuric
acid of such a strength that one c.c. equals one milligram of
carbon dioxide (see appendix B), and barium hydroxide solu-
tion of approximately equal strength. Since it is impracticable
to prepare exact solutions of barium hydroxide, and to keep
them without change, the exact value of the barium hydroxide
solution must be found by titration against the standard sul-
phuric acid. This standardization, as well as the subsequent
titration, is best made in a small flask to lessen the error from
absorption of carbon dioxide from the air. It will be found
most generally satisfactory to measure into the flask about 25
c.c. of the barium hydroxide, add a drop of phenolphthalein
solution, and titrate with the sulphuric acid to the disappear-
ance of the pink color. In all cases the first end-point should
be taken as the correct one, because the pink color will some-
times return on standing.

The apparatus consists of the collecting bottles, 50 c.c. bu-
rettes, a stoppered bottle of hard glass of 40 c.c. capacity, and
a 25 c.c. pipette.

Procedure. — Remove the cap from the tube in the stopper
of the bottle, insert the tip of the burette so that it projects into
the bottle, and run in rapidly 50 c.c. of barium hydroxide from
the burette. Replace the cap, place the bottle on its side and
roll or shake it at frequent intervals for 45 minutes, taking care
that the whole surface of the bottle is moistened with the solu-
tion each time. At the end of this time thoroughly shake the
bottle to mix the solution, remove the cap, and pour the solu-
tion into a stoppered bottle of hard glass of 40 c.c. capacity,
taking care that the solution shall come in contact with the air
as little as possible. Under these conditions a full well-stoppered
bottle may safely stand for days before titration. For the
titration, measure out with a pipette 25 c.c. of the clear liquid

AIR: ANALYTICAL METHODS 35

into a 75 c.c. flask and titrate it with the sulphuric acid as in
the standardization.

The calculation is similar to that given under the Walker
method except that it should be remembered that only one-
half of the barium hydroxide was used in the titration.

Rapid Methods. — In addition to the above methods for de-
termining carbon dioxide just described, there are general tests
which can often be used with advantage. If within the space
of a few hours some 50 or more tests are to be made, and com-
parative results rather than great accuracy are required, some
simpler form of apparatus is desirable.

Such an apparatus, to be satisfactory, should meet, so far as
possible, the following requirements:

(i) It should be sufficiently compact and portable to be car-
ried in the hand from place to place.

(2) It should be as simple in construction as possible, and its
use should not involve delicate measurements.

(3) If possible, the apparatus should be made entirely of glass,
avoiding prolonged contact of corks or of rubber connectors
with any dilute solution which may be used.

(4) It should be so constructed as to protect the solution at
all times from the carbon dioxide of the air, especially whOe the
determination is being made, because of necessity such an ap-
paratus must be used within the area of contamination.

(5) The complete apparatus should be sufiicient for 50 or
more determinations.

(6) It must be capable of giving results of a reasonable de-
gree of accuracy, say within 0.5 part of carbon dioxide in 10,000
parts of air, in the hands of persons having little or no chemical
knowledge and minimum skill in manipulation.

(7) If a solution be used in the apparatus it should be one
which can be prepared easily from chemicals readily obtained;
the solution must maintain its efficiency for a reasonable length
of time, if protected from external influences; and the solution
should be one that is not at all dangerous or obnoxious to use.

Simplicity of apparatus is much to be desired, but it should

AIR, WATER, AND FOOD

not be gained at too great sacrifice of accuracy. Even when no
greater precision is required than is necessary to meet the de-
mands of practical work, it is out of the question to measure the
test solution by means of an ordinary pipette or to preserve it
for any length of time in stoppered vials; the strength of the
solution is almost certain to be reduced by contamination with
the breath, or by contact with rubber or cork.

It must ever be borne in mind that extreme care is necessary
in the preparation and use of these very dilute solutions, the
strict observance of conditions which might well be neglected
in ordinary analytical procedures being here an essential factor
of success.

For the preservation and measuring of the test solution an
apparatus has been devised which appears to answer the above
requirements, and in actual practice has been found satisfactory.*

The essential feature of this
apparatus consists of an auto-
matic pipette for measuring
the test solution. This is a
modified form of the pipette
first proposed by G. P. Vanier
and in use in this laboratory
for a number of years. A
general idea of it may be had
from Fig. 5. The manner of
using it is extremely simple.
The test solution is preserved
in a one-liter bottle of hard
glass provided with a doubly
perforated rubber stopper.
Through one opening passes
the siphon tube of the pipette, which is sufficiently long to reach
to the bottom of the bottle; through the other passes a glass
tube ending just below the stopper and connected with a small

* "Air Testing for Engineers," A. G. Woodman and Ellen H. Richards, Tech.
Quay., 1901, 14, p. 94.

Fig. 5.

AIR: ANALYTICAL METHODS 37

drying tube containing fresh soda-lime. By means of the three-
way cock the solution is allowed to flow into the small inside
pipette until it overflows. The stop cock is then turned, and
the solution allowed to flow out at the lowest point. The pipette
is made of such a size as to deliver exactly lo c.c. The excess
of liquid which accumulates in the ov^erflow reser\'oir may be
drawn off when desired. The bottle and pipette are contained
in a wooden case, about 20 by 8 by 7 inches, outside dimen-
sions, and with the solution, weigh about eight pounds. The
case is furnished with a handle at the top so that it may be
carried readily in the hand from place to place. The bottle
is fastened to the case, and the lower end of the pipette is
clamped to a wooden support to keep it from swinging. The
stopper should be firmly fastened to prevent loosening.

The bottle should be thoroughly cleaned and washed with
potassium bichromate and sulphuric acid, and it is best also to
steam it for half an hour or so. As a further measure of pre-
caution the rubber stopper is boiled with dilute caustic potash
and thoroughly washed, although the solution can come in con-
tact with it only through splashing while the case is being
carried.

This measuring apparatus may be used with a variety of
methods, and with various strengths of solution.

Cohen and Appleyard Method.* — Principle. — The method
of Cohen and Appleyard is based upon the fact that if a dilute
solution of lime-water, slightly colored with phenolphthalcin, is
brought in contact with a sample of air containing more than
enough carbon dioxide to combine with all the lime present, the
solution will be gradually decolorized, the length of time re-
quired depending upon the amount of carbon dioxide present.
That is, the quantity of lime-water and the volume of air re-
maining the same in each case, the rate of decolorization will
vary inversely with the amount of carbon dioxide.

Reagents and Apparatus. — The solution used is a dUute so-
lution of lime-water colored with phenolphthalcin. To freshly
* Chcm. News, 1894, 70, p. iii.

38 AIR, WATER, AND FOOD

slaked lime add 20 times its weight of water in a bottle of such
size that it is not more than two-thirds full. Shake the mix-
ture continuously for 20 minutes, and then allow it to settle
over night or until perfectly clear. The resulting solution is the
stock lime solution, or " saturated lime-water." If made in the
manner indicated, each cubic centimeter of it ought to be very
nearly equivalent to one milligram of carbon dioxide. If, how-
ever, it is desired to know the strength of it more exactly, it
may be determined by standard acid.

To prepare the " test solution," pour into the one-liter bottle
of the testing apparatus one measured liter of distilled water,
and add 2.5 c.c. of a solution of phenolphthalein (made by dis-
solving 0.7 gram of phenolphthalein in 50 c.c. of alcohol and
adding an equal volume of water). Stand the bottle on a sheet
of white paper and add the '' saturated lime-water " drop by
drop from a pipette, shaking the bottle thoroughly after each
addition until a faint pink color is produced which is permanent
for one minute. Now add 6.3 c.c. of the ''saturated lime-water,"
shake, and immediately connect the bottle again to the apparatus.

For accuracy in air which is high in carbon dioxide, it is found
advantageous to use a solution which is twice as strong as the
above. This double solution is prepared in precisely the same
way, using 5.0 c.c. of the phenolphthalein solution and 12.6 c.c.
of the " saturated lime-water."

While this procedure does not give an exact volume of solu-
tion, it is believed to be the best for the preparation of this
dilute test solution, since it obviates the necessity for pouring
the prepared solution from the measuring flask into the bottle
in which it is kept; 12.6 c.c. of the stock lime solution is added
rather than 10 c.c, in order to keep the values obtained with
the resulting solution more nearly comparable with the older
values calculated on the supposition that 10 c.c. of the " satu-
rated lime-water " was equivalent to 12.6 mg. of carbon dioxide.

The apparatus used is that shown in Fig. 5. The samples are
collected in 500 c.c. bottles by either the water displacement or
steam vacuum method.

AIR: ANALYTICAL METHOD

Procedure. — Remove the rubber stopper from the bottle con-
taining the sample of air; run in quickly by means of the auto-
matic pipette lo c.c. of the standard test solution; note the
time; replace the stopper; shake continuously and vigorously
until the pink color disappears; and again note the time. The
disappearance of color can most easily be seen if the bottle is
held over a piece of white paper. From the time required for
the pink color to disappear, the amount of carbon dioxide may
be found from Table A.

TABLE A

Time,
minutes

and
seconds.

Standard

solution.

CO2 in

10,000.

Double

solution.

COjin

10,000.

Time,
minutes

and
seconds.

Double

solution.

COjin

10,000.

O.IS
0.30

0.45
1 .00

IIS
1.30
1-45
2.00

2. IS
2.30

2.4s
3.00

31S

3-45
4.00

41S
430
4-45
5.00

S15
S-30

"iS-6'
12. 1
9.9
8.4

7.2

6.3

4-9
4-4
4.0
3-8
3-7
3-6

S-45
6.00

6.15
6.30

6.4S
7.00

71S
7-3°

4.0
3-9

3-7

13
II
10

7
7
6
6
S
5
5
4
4
4
4
4
4

4
I

3
6
0

5
I

7
4

7
S
3

2
I

Shaker Methods. — At least two forms of apparatus are on
the market for determining the percentage of carbon dioxide by
measuring the amount of air required to decolorize the stand-
ard solutions described on page 38. These are known as the
Fitz and the Wolpert Shakers (see Fig. 6). The results obtained
are less accurate and more uncertain than by other methods,
but if great care is taken to keep the apparatus at some

AIR, WATER, AND FOOD

distance from the face of the worker, approximate results can
be obtained. As both shakers operate on the same principle
only the Fitz will be described. It consists of a tube of about
30 c.c. capacity, closed at one end, and graduated for a dis-
tance of 20 c.c. from the closed end. In this
tube, by means of a rubber collar, slides a smaller
tube which is contracted at the outer end so as
to be more readily closed by the linger.

Procedure. — See that the inner tube of the
shaker slides readily in the outer one, moistening
the rubber collar slightly if necessary. Have
the inner tube pressed down to the bottom of
the larger one and measure into the apparatus
10 c.c. of the test solution from the automatic
pipette. Pull the inner tube up to the 5 c.c.
mark (the bottom of the inner tube serving as
the index) and close the end of the tube with
the finger. Hold the apparatus horizontally,
and shake it vigorously for exactly 30 seconds.
The amount of air that is thus brought in contact with the
solution is equivalent to approximately 30 c.c, as there are
25 c.c. of air above the liquid when the small tube is forced to
bottom of the larger. Remove the finger, press down the small
tube again to the bottom of the larger and draw it up to the
20 c.c. mark. Shake the apparatus again for 30 seconds. The
amount of air brought in contact with the solution is now
30 + 20 = 50 c.c. Repeat the shaking, using 20 c.c. of fresh
air each time, until the pink color is discharged. The amount
of carbon dioxide corresponding to the number of cubic centi-
meters of air used will be found in Table B.

Carbon Monoxide. — The detection and estimation of carbon
monoxide in the very minute quantities in which it is found in
the air of ordinary rooms is a problem of considerable difficulty.
Detection. — Probably the most convenient test for detecting
small quantities is the blood test. Dilute a large drop of human
blood, freshly drawn by pricking the finger, to 10 c.c. with water.

Fig. 6. Fitz
Shaker

AIR: ANALYTICAL METHODS

Divide the solution into two equal portions, and shake one
portion gently for 10 minutes in a bottle containing about
100 c.c. of the air to be tested. Compare the tints of the two
portions by holding them against a well-lighted white surface.
The presence of carbon monoxide is indicated by the appear-

TABLE B

Cubic centimeters
of air.

Standard test
solution.

Double

solution.

COj in 10,000.

CO2 in 10,000.

15-6

22.2

12.4

10.2

8.7

13'^

7-5

150

6.6

170

5-8

190

5-2

210

4.8

230

4-S

250

4-3

270

290

3-95

310

3-8

330

3-7

350

3-6

370
390
410

4
4
4
4
4
3

7
S
4
2

45°
490

530

ance of a pink tint in the blood which has been shaken with air.
One part in 10,000 can be detected in this way.* The dcHcacy
of the test can be increased by examining the blood, after shak-
ing with air, with a spectroscope. By collecting the sample in a
eight-liter bottle and examining it in this way o.oi part in 10,000
may be detected.

Determination. — Practically all the methods for the dctcmii-
nation of carbon monoxide in small amounts depend on the
equation:

l205-t-5CO->5CO> + L;

* Clowes, "Detection and Estimation of Inflammable Gas and \'apor in the
Air," p. 138.

42 AIR, WATER, AND FOOD

then either the iodine * is titrated or the carbon dioxide deter-
mined. The method consists of passing the air through U-tubes
containing potassimn hydroxide and sulphuric acid to remove
unsaturated hydrocarbons, hydrogen sulphide, etc., and then
through a U-tube containing iodine pentoxide, and heated to
150° C. The iodine liberated is absorbed in a solution of potas-
sium iodide, and may be titrated with N/iooo sodium thiosul-
phate, or the carbon dioxide passing through the potassium
iodide may be absorbed by barium hydroxide and determined. f

Nitrites. — ■ The determination of the amount of nitrites or
nitrous acid in the air can be readily made as follows: Collect
a sample of the air in a calibrated eight-liter bottle, as in the
determination of carbon dioxide. Add 100 c.c. of approxi-
mately N/50 sodium hydroxide solution. (This should be free
from nitrites, and is best made by dissolving metallic sodium
in redistilled water.) Shake the bottle occasionally and let it
stand for about 24 hours. Take out 50 c.c. of the solution and
determine the amount of nitrites as directed in the determination
of nitrites in water.

Micro-organisms.J — The determination of bacteria in the
air is of importance only under special conditions which some-
times exist in dairies, factories, etc. In general the method used
is to filter a measured amount of air through sand, shake out
the bacteria with sterile water, and plate aliquot portions.
Counts are made after 5 days' incubation at 20° C.

* Kinnicutt and Sanford, J. Am. Chem. Soc, 1900, 22, p. 14.
Morgan and McWhorter, J. Am. Chem. Soc, 1907, 29, p. 1589.
Seidell, /. Ind. Eng. Chem., 1914, 6, p. 321.
Gautier, J. Gas Lighting, 121, p. 547.
t For details of the methods reference should be made to the above articles.
Recently a portable apparatus has been described by Goutal, Analyst, 19 10, 35,
p. 130.

X See "Standard Methods for the Bacterial Examination of Air," Am. J. Pub.
Health, 1910, 6, No. 3, or reprint by the Am. Pub. Health Assn.

CHAPTER IV
water: its relation to health, its sources and properties

Two-thirds of the animal organism consists of water; this
water is necessary * for practically all physiological processes,
either taking part in the reaction or acting as a solvent. It aids
in carrying nourishment to all parts of the body and in disposing
of the waste products formed. The evaporation of water from
the surface of the body serves as the most important method
of regulating the body temperature. Since water is lost by
these means as well as during respiration, it is evident that the
animal organism must be supplied with water from outside
sources. The daily amount needed for each person is five or
six pints. This water is derived in part from food which, as
eaten, contains from 30 to 95 per cent; in part from boiled
water, as in tea and coffee; or raw from well or city tap.

Water is also required for many other purposes, such as cook-
ing, washing, generation of power, and other manufacturing
uses. It has been estimated that 25 gallons per person per day
is sufficient for household purposes. Then some must be al-
lowed for public use and a rather large amount for manufactur-
ing. For cities in this country amounts varying from 50 to
200 gallons are used, with an average of close to 100 gallons.
This is about three times as much as is used in European cities,
and undoubtedly a large amount represents unnecessary waste.
That this is true is shown by the fact that when the individuals
in a community are required to pay for the actual amount of
water consumed, which is done through the introduction of
meters, the consumption falls off to one-half or one-third of the
former quantity used. Waste of water represents a very serious
problem in large cities, where it is often necessary to go long

* See " Text-book of Physiological Chemistry," .\bderhalden-HaU, John Wiley
& Sons, 1908, p. 354.

44 AIR, WATER, AND FOOD

distances at great expense, to obtain a sufficiently large supply
suitable for drinking purposes.

The problem is made still more difficult by the use of large
bodies of water, both lakes. and rivers, for the purposes of waste
disposal. Recent reports of experts * have raised the question
as to how much of the expense of purifying a sewage should be
borne by the community emptying its waste into a stream, and
how much should be borne by a community farther down the
stream where water is removed for domestic use. The only
certain condition which should be demanded is that wastes
should be in such a state and so diluted that no nuisance will
be created along the banks of the stream. It seems as if the
question of further purification would have to be decided for
each individual case as it arises.

That there is a close relation between drinking water and
disease has long been suspected, but it is only since the develop-
ment of the present ideas of the cause of disease that this
relationship has been satisfactorily demonstrated. Drinking
water may act as the carrier of the germs of at least two well
defined diseases, — Asiatic cholera and typhoid fever, — and
probably of those of other intestinal troubles. There is, be-
sides, some tendency to disturb the system when a change is
made from one kind of drinking water to another of radically
different composition, such, for example, as a change from a
hard Middle West water to a soft New England water. The
disturbance is generally only temporary, as the system becomes
rapidly accustomed to new conditions.

The first cholera epidemic to be traced definitely to drinking
water was that in London in 1854, which centered about the
Broad Street Pump, and the investigation of which was thor-
oughly carried out by an efficient health officer. Since then
numerous epidemics have been traced to the use of polluted
water, notably that of Hamburg in 1892-3. f

* See, for example, Eng. Rec, 191 2, 65, p. 209.

t For a description of epidemics of both cholera and typhoid fever see Sedg-
wick's "Sanitary Science and Public Health."

WATER 45

In this country we have little to fear from cholera on account
of the efficient work of the Public Health Service at our ports,
but typhoid fever is still a scourge and a disgrace. As early as
1850 it was maintained by Budd in England that this fever was
spread by drinking water, but no sufficient evidence was pro-
duced until the Lausen, Switzerland, epidemic of 1872. The
first large epidemic in this country to be traced to water was that
of Plymouth, Pa., in 1885, in which about 1000 cases resulted
from the negligence of an attendant on one typhoid patient.
Since that time numerous small and large epidemics have been
traced with more or less certainty to the use of polluted water.

That the introduction of a good water supply in place of a
bad one results in a marked decrease in t}'phoid fever can be
readily seen by almost endless lists of statistics of cities and
towns which have cither obtained a new supply or have intro-
duced filters, the deaths from typhoid being from one-half to
one-fifth of the number formerly recorded in such places.*

Not only does the introduction of unpolluted water mean a
decrease in typhoid fever, but there seems also to be a general
increase in the health of the community. This effect was
noticed at about the same time by ISIills in this country and
Reincke in Germany, and is known as the Mills-Reincke phe-
nomenon. Hazen attempted to formulate a mathematical re-
lationship between the decrease in typhoid fever and that in all
other diseases, but the result is merely an approximation. This
increase in the general health may be due to increased vitality
by the elimination of one disease. It has been recently sug-
gested that since tuberculosis is hable to follow typhoid fever,
a decrease in the latter would account for a decrease in the
former.

Safe water, is, therefore, one of the necessary requirements of
any community, large or small.

Rain Water. — Let us trace the cycle through which water
passes, and point out the sources of supply, and the methods of
contamination. Water vapor rising from the sea and land con-

* See Am. J. Pub. Health, 1913, 3. P- 1327-

46 AIR, WATER, AND FOOD

denses and falls to the earth as rain. As it does so, ammonia,
carbon dioxide, and other soluble gases are absorbed, and dust
and living organisms are collected. As soon as these sub-
stances are removed from the air, the rain water becomes a
very pure source of supply, and can be used for drinking pur-
poses if properly stored. There are several factors to be ob-
served in this. First, there should be no connection whatever
between the storage tank and any drain or sewer from a house
or barn. More than one case of typhoid fever has resulted
from the backing up of sewage through an overflow pipe into a
rain water tank. Second, no metal or other material which
is injurious to health should be used in building such a tank,
as rain water is soft and often slightly acid and, therefore,
has considerable solvent power for most metals. The best ma-
terials to use are cement, slate, or stoneware; lead should be
absolutely avoided, and zinc will not last any length of time.
Third, there should be some method of wasting the first rain
that falls, in order not to load the storage tank with dirt and
other material which may come from a roof or collecting shed,
and render the water unpalatable. Fourth, there should be
some easy means of cleaning the tank, and this should be done
at frequent intervals. Rain water is used for drinking practi-
cally only in tropical regions.

Surface Waters. — Approximately one-third of the rain evapo-
rates again from the surface where it falls; another third runs
off on the surface, forming streams, rivers, and lakes, finally
reaching the ocean; the other third sinks into the ground, per-
haps joining the surface waters underground, coming out as
springs or flowing wells, or remaining in the soil. The average
rainfall for the whole United States is about 36 inches, varying
in different parts of the country from almost nothing to 60
inches. Thus we find the amount of water with which we have
to deal is very variable, depending on the locality and the
season. Approximately one-half of the rainfall finds its way
finally into rivers, either running off on the surface, or entering
from underground.

WATER 47

Surface waters form an exceedingly important source of
supplies, as most large cities fmd them necessary on account
of the large quantities of water required. Water from small
streams and brooks on a water shed may be collected and stored
in reservoirs. This method is considerably used, particularly in
hilly regions, and if proper care is taken to prevent any pollution
on the watershed, sufficient supplies of excellent quahty may be
obtained. The reservoirs are generally uncovered, and should
be stripped of all plant life. Surface water, if unpolluted,
usually improves on storage.

Where it is not possible to obtain a supply in this manner,
large rivers or lakes are used. These are nearly all subject to
more or less pollution, and in general the water should not
be used unless filtered or sterilized. Some self-purification will
take place in such bodies of water.* The most important
factor in such purification is the removal of bacteria by means
of sedimentation, the larger particles in the water carrying
bacteria with them to the bottom of the stream where the patho-
genic varieties soon die out. Thus in a slow moving stream
harmful organisms are removed more quickly than in a rapidly
moving river. Another important factor is the exhaustion of
the food supply. Also, conditions of temperature are not favor-
able for the growth of many bacteria, and it is undoubtedly
true that even in a highly polluted water there is little multi-
plication, and much dying off of disease organisms.

On the other hand, it is not safe to rely on self-purification,
particularly when the health of a large number of people is at
stake. There are too many possibilities of accidental pollution.
Some artificial means must be used. These will be mentioned
later.

Odors sometimes develop in stored water as a result of growth
of various plants and animals.f Some of these odors are ex-

* See Jordan, "Natural-purification of Streams." Paper presented at the :;6th
annual convention of the American Water Works Assn.

t See Whipple, "The Microscopy of Drinking Water," John Wiley & Sons,
1914.

48 AIR, WATER, AND FOOD

ceedingly disagreeable and may render a water supply unfit to
deliver. The growths can generally be exterminated by the
proper use of copper sulphate in quantities which will kill the
small organisms but are not injurious to the human system (one
part to from one to 20 million parts of water).

Surface waters often have color, produced usually by solu-
tion, in colloidal form, of partly decomposed vegetable matter,
which is perfectly harmless, and such waters should not be con-
demned unless sewage is also present. They are, however, often
decolorized, before delivery, by means of alum. Surface waters
are generally softer than ground waters, have a shght, but not
disagreeable odor, may be more or less turbid, and in the sum-
mer time are Hable to be warmer than is desirable. On the
whole, however, there is no more satisfactory supply for a large
city than a good surface water.

Ground Waters. — From 25 to 40 per cent of the annual rain-
fall in temperate regions soaks at once into the ground, and
passing downward through the soil to hardpan, to clayey or
impervious layers, or to rock surface, thence through crevices,
broken joints, or glacial drift-deposits to the water-table, flows
along the slope for many miles until it finds its way again to
the surface, either from the bottom of a lake, the bed of a river,
the side of a hill, supplpng wells or appearing as springs. In
any one of these courses it may be intercepted by man and
caught or pumped for his use. Such water may never have
been far from the surface; it may have been used and returned
to the ground many times; it may have appeared as surface-
water and again disappeared to great depths. It has been esti-
mated that water moves in the ground at rates varying from
0.2 to 20 feet per day. This movement is in the form of a sheet,
and its rapidity as well as the amount of water held in the
ground will depend on the geological formation. Thus a clay
will hold more water than loam or sand, while the permeabihty
is just the reverse, clay being nearly impermeable. Water also
passes through channels in rocks, either made by the water it-
self or consisting of cracks and fissures. These latter are often

WATER 49

a source of danger, as no purification can take place if a pol-
luted water travels in this manner.

This long contact with rocks will, of course, bring mineral
substances into solution which may be precipitated as new
rocks are reached or other streams encountered, so that the
same gallon of water may have had many stages in its course,
and may have held many different substances in solution. It is
no wonder that so active a solvent as water should take with it
much substance whenever it remains long in contact with soil
or rock, for it may be months before that which has once sunk
out of sight again appears. In fact, great rivers are supposed to
flow into the sea from under the surface. Tljjen, too, the acquisi-
tion of dissolved gases favors the so^ation of many substances;
for instance, water carrying carbour dioxide dissolves limestone.

From a chemical standpoint ground waters may be divided
into two classes, — (i) springs and shallow wells (those 30 feet
or less in depth) and (2) deep and artesian wells. In general
springs and shallow wells yield softer water than deep wells of
the same region, but they are much more subject to pollution
than the latter, which, if built so as to exclude any surface
water, are usually a safe source of supply. Pollution does
sometimes enter a deep well, due to the passage of water
through fissures and crevices in the rocks.

The greatest source of danger is the shallow well. This should
never be used in a thickly populated region, and in country
districts only when it can be placed in such a position that there
can be no connection through the ground with a privy or cess-
pool. A well should be built in such a manner that no surface
water can enter it, and the walls should be tight to a depth of
five to 10 feet below the surface in order that any water which
sinks into the ground may be sufficiently filtered before enter-
ing the well. The area from which a well ma}' draw varies
with the permeability of the soil, and may have a diameter of
20 or more times the depth of the well. The ground which is
influenced by a well is in the form of an inverted cone whose
apex is at the bottom of the well.

50 AIR, WATER, AND FOOD

If a well is found upon examination to be polluted with sew-
age it is often desirable to find the source of trouble in order
to stop further pollution. There are several methods of doing
this.* A survey of the ground and the conditions surrounding
the well is often sufficient to indicate the probable sources, but
more definite evidence may be required. Some substance is
then added to the suspected source, washed into the ground
with a large amount of water, and the well examined for the ap-
pearance of the substance. For this purpose bacteria, such as
B. prodigiosus and B. violaceous, can be used. These organisms
are easily grown, are harmless and can readily be identified.
If these do not reach the well from the suspected source of
pollution it is fair to assume that no pathogenic organisms
will do so, but will be filtered out in passing through the
ground. The only uncertainty with this method is that while
the bacteria may be sufficiently removed at the time of the test,
the filter may sometime break down and allow sewage organ-
isms, and possibly disease germs, to enter the well. It is, there-
fore, better not to use a well water which receives sewage from
any nearby source, even though bacteria are being eliminated
in passing through the ground.

Other methods of tracing the source of pollution are by the
use of common salt, easily tested in the well water by an analysis
for chloride; lithium or strontium salts, recognized even in
minute amounts by means of the spectroscope; and fluorescent
dyes such as fluorescein, which are readily observed in a glass
of water.

One method of obtaining ground water in comparatively
large quantities is by means of the so-called "filter gallery."
This consists of a series of wells dug near the banks of a river.
It was originally thought that a suction would be created so as
to draw water from the river into the wells through a layer of
soil sufficient to remove harmful bacteria. As a matter of fact,
the filter gallery actually operates by intercepting ground water

* See Thresh, "Examination of Waters and Water Supplies," 2nd edition, pp.

25-34-

WATER 51

on its way to the river, really a better method than had been
intended. In sparsely populated regions where the ground
water is unpolluted, good results have been and are being ob-
tained by the filter-gallery, but when a region becomes thickly
settled considerable danger results. Furthermore, in times of
drought water may be drawn from the river bed, and if this
reaches the gallery improperly filtered, a typhoid epidemic
may result.*

In general, good ground waters contain more mineral matter
than surface waters, have no color or odor, can be delivered at
a lower temperature, and are often more palatable than surface
waters. It is, however, more difficult to obtain large supplies
from the ground, and, therefore, only comparatively small com-
munities can avail themselves of such sources.

Water Purification. — Water in passing through the ground
may undergo a number of changes in its dissolved and suspended
constituents. If this water contains sewage it will carry, with
other suspended matter, a large number of bacteria, some of
which may be of pathogenic varieties. If the polluted water
passes through not too coarse soil, the bacteria will be held by
the soil, and thus dangerous disease germs will probably be re-
moved. Even if all the sewage bacteria are not removed there
will still be some protection against disease, because disease
organisms have, in general, less vitality to withstand unfavor-
able conditions as well as being present in smaller numbers than
less harmful varieties. However, there is still some chance of
these bacteria being present at times, and it is, therefore, not
advisable to use water in which sewage organisms are present.

In streams, as has already been noted, pathogenic bacteria
gradually settle to the bottom and die out.

Thus there is some natural protection against the spread of
disease by means of drinking water, but it is not safe to depend
on such protection, particularly where the health of a com-
munity of people is involved. If a water suppl}' which is sub-

* See "Typhoid Fever in Des Moines, Iowa," /. Am. Med. Assn., 191 1, 56,
p. 41.

52 AIR, WATER, AND FOOD

ject to either continuous or intermittent pollution has to be
used, some method of artificial purification is required before it
can be safely used for drinking purposes.*

There are two general methods of filtering water on a large
scale. The first is known as slow sand filtration. In this
method the water is run through a layer of sand from two to
four feet thick, supported by gravel and properly underdrained.
The filter beds are generally built in units of one acre each, and
may be covered or not depending on the climatic conditions.
Previous to filtration the water may be screened and stored in
reservoirs to allow some removal of suspended matter, includ-
ing bacteria. As the water passes through the sand a layer of
slimy material gradually collects on the surface, which acts as
the real straining medium and holds the bacteria. As this
material collects the rate of filtration decreases until a point is
reached where it is uneconomical to continue. The water is
then allowed to drain out from the sand, the top layer scraped
off, and the filter again started. The sand removed is washed
and returned to the filter about once a year. A slow sand filter
operates at rates of from one and a half to three million gallons
per acre per day, and is probably the most efficient method of
removing bacteria on a large scale. It does not, however, com-
pletely remove color or odor.

The other method is that known as rapid filtration (also, un-
fortunately, termed mechanical filtration). Instead of allowing
the filtering layer to form from the matter in the water as in
slow sand filtration, a coagulant, generally alum, is added to
the water. The alkali, originally present, or added, precipi-
tates aluminum hydroxide which coagulates the suspended par-
ticles and removes the color. Part of the hydroxide is allowed
to settle out and the remainder is put on a filter built of sand,
where it collects on the surface and forms the filtering medium.
The filters are washed about every eight hours by reversing the
flow of water and agitating the sand by means of rakes or com-
pressed air. Filtration takes place much more rapidly by this

* See Hazen, "The Filtration of Public Water Supplies."

WATER 53

method, being at rates from loo to 150 million gallons per acre
per day. If there is insufficient alkali present naturally in the
water enough must be added, usually either as sodium carbon-
ate or as calcium carbonate, to completely precipitate the alum
and leave some alkali in excess. Alum, being acid, if allowed
to remain in the water renders it corrosive. The amounts of
alum used vary from one-tenth to three grains per gallon of
water.

Rapid filtration does not give quite as high a bacterial removal
as slow filtration, but it is much more efficient in removing
turbidity and particularly color. It requires a smaller invest-
ment and occupies less ground for the same amount of water
filtered. With either method expert control is necessary in
order to obtain satisfactory results.

A number of filters on the same principle as just described,
but built in small units, are on the market, intended to supply
hotels, manufacturing establishments, swimming pools, etc.
Many of them give reasonably good results when properly
operated, but they never should be considered to be automatic
in character. They all need careful attention.

Filters still smaller are sold for office and household uses.
These generally consist of artificial stone or porcelain through
which the water is forced, such as the Pasteur-Chamberlain or
the Berkefeld filter. If the stone, or candle as it is called, is in
good condition, sterile water may be drawn when the filter is
first put into use, but the bacteria lodging in the stone grad-
ually develop and may grow through the filter so that as water
passes through it will wash bacteria with it. It must be ad-
mitted that the chances are that pathogenic organisms will not
get through. If, however, there is a crack in the candle, often
too small a one to be visible, the filter will allow all kinds of
bacteria to pass. One of the great objections to the use of such
filters is the false feeling of safet}' which they may inspire in
the owners. The all too common small "filter" which screws
on the faucet is not only useless, but worse.

If unsafe drinking water must be used in a house, the onlv

54 AIR, WATER, AND FOOD

sure method is to bring the water to a boil. This is sufficient to
kill any harmful intestinal organisms. Small stills which can
be placed on the back of the stove are of service in this con-
nection. The fiat taste of boiled water may be removed by the
addition of a pinch of salt or by aeration.

Sterilization of Water. — Where a badly polluted supply is
used, or extreme caution is desirable, or where a good supply
suddenly becomes polluted and emergency measures deemed
wise, disinfection may be resorted to. The most practical
method is by the use of compounds of chlorine, — hypochlorite
of lime (chloride of lime or bleaching powder), sodium hypo-
chlorite (electrolytic bleach), or chlorine gas itself. Of these
the cheapest under ordinary conditions is chloride of lime.
This has the disadvantage of being disagreable to handle, and
of not dissolving completely in water. Amounts of from -^^ to
^Q grains per gallon are generally sufficient. Sodium hypo-
chlorite can be used where there is cheap electricity, as it is
made by passing a current through a solution of common salt.
The use of chlorine gas is a recent development and appears to
be giving satisfactory results, although considerably more ex-
pensive than the other methods.

None of these substances, in the quantities used, are in any
way harmful. Where large doses are given complaints are
sometimes received that they can be tasted in the water, but,
even if true, this is not a necessary consequence of their use.
The disinfecting action is probably due to the chlorine itself.

Electrical methods of sterilization are also in somewhat
limited use. One of these is through the formation of ozone by
an electrical discharge through air, and treatment of the water
with the ozonized air. Ozone, in the presence of water, is a
reasonably good disinfectant, but its cost makes it prohibitive in
most places, and its application to the water presents some
engineering difficulty. The largest plant working is probably
that at St. Petersburg.*

A more recent development than ozone is the use of ultra-

* See Tillmans-Taylor, "Water Purification and Sewage Disposal."

WATER 55

violet light, as obtained by the quartz-mercury-vapor lamp.
Ultraviolet light is a good disinfectant, but it is expensive to
produce in most places, and there are difficulties in applying it
to waters of all characters. The rays will not penetrate a turbid
or colored water to any extent, and, therefore, preliminary filtra-
tion and decolorization is often necessary. This, of course, adds
greatly to the expense. The method may, however, fmd use in
the future, if it is possible to produce it for a reasonable amount.
Ice. — Questions are often asked concerning the use of ice
in drinking water. In general, natural ice, particularly when
stored from four to eight months, is comparatively safe. In
freezing, suspended and dissolved matter is not removed from
the water with the ice, except a small amount mechanically
enclosed. Furthermore, it has been shown that over 90 per
cent of sewage bacteria die out on storage. Artiticial ice, if
made from polluted water, is not safe, as in the method used all
suspended matter is frozen into the center of the cake. If the
artificial ice is made from unpolluted or from distilled water
as it should be, it is, of course, perfectly safe to use for all
purposes.

CHAPTER V

SAFE WATER AND THE INTERPRETATION OF ANALYSES

Pure water, such as may be found in the laboratory, is neither
necessary nor probably desirable for drinking. There are, how-
ever, certain requirements which should be borne in mind in
looking for a supply. First, the water should be free from sew-
age and all other waste products. Second, it should not con-
tain an excessive amount of mineral matter. Third, it should
be free from color, odor, taste and suspended matter, and
should be delivered at a temperature not over 15° C. It is
obvious that all of these requirements cannot always be lived
up to, but it is essential that the first one should be, even at the
expense of the other two. A water free from sewage and other
waste products can be called a ''safe" water. Unfortunately,
physical appearance is taken as the criterion of the safety of a
supply by too many people. The cool, clear, colorless water is
much to be preferred to the safe colored or muddy one; and it
is sometimes difficult to persuade the user of such a supply as
the former that he may be endangering his health by drink-
ing it when tests have shown the presence of sewage. Since
appearance is of such importance, it is necessary to take this
into account in any water examination.

Since, as already described, a water once in contact with
sewage may become purified and be rendered safe for drinking
purposes, and since water is so universally made a carrier of
refuse that it is difficult to find a stream or well which has nev^er
been at any time in contact with waste, certain arbitrary stand-
ards have been chosen to determine when a water may be called
safe, on the basis of an analysis. Such limits are very mislead-
ing of themselves, especially if used over a wide extent of ter-
ritory. The English standards, for instance, are not applicable

SAFE WATER 57

to eastern North America. Only a study of all local conditions
and a wise interpretation of all results can make standard
figures of any significance. This is true, also, of bacterial re-
sults in surface waters. In lakes and streams there are so
many varieties of bacteria present and in such varying numbers,
according to wind and rain and water-shed, that taken alone
the numerical count gives no more convincing proof than is
found in chemical figures.

While it is quite within the limits of possibility that a cul-
ture-tube of typhoid bacilU might be emptied into the middle
of a river or be washed into a reservoir, and chemical analysis
give no sign, yet no continuous natural means of contamination
is known which is not accompanied by substances readily de-
tected by suitable chemical examination.

Sanitary Examination. — The examination of a water to de-
termine its safety for domestic use is called a sanitary analysis,
in distinction from that examination which determines its fit-
ness for manufacturing purposes, for use in steam boilers, or its
medicinal value. Such an examination may be either bacterio-
logical or chemical in character, but the object in either case is
the same, that is, to determine the absence of sewage or its
presence in quantities sufl'icient to render the water dangerous
to drink. In neither kind of examination are the harmful sub-
stances themselves sought for. Typhoid organisms have been
isolated from water during epidemics in only a few cases and
the process is a long and tedious one. Furthermore, such a
search would often be useless for an infected person does not
usually come down with the disease until lo to 14 days after
infection, and the organisms might have died during this time.
Also, one does not care to wait until an epidemic starts before
examining the water supply, but desires to know in advance
whether or not there is any possibility of trouble. The presence
or absence of sewage determines this possibility.

In a bacteriological examination, the presence of sewag.c is
determined first, by counting the total number of bacteria per
cubic centimeter, and second, by looking for some type of dis-

S8 AIR, WATER, AND FOOD

tinctly sewage organism, such as B. coli. The total count has
little signilicance in a surface water, but in a well or filtered
water, should not be over loo bacteria per cubic centimeter.
B. coli should not be present in numbers of one or more per
cubic centimeter. Considerable discussion surrounds the de-
termination of this organism, but it is quite impossible to see
what difference it makes whether the bacteria isolated show all
the typical reactions of B. coli communis or not. The members
of the colon group get into a water supply practically only with
sewage, and it should not make any difference in the interpre-
tation of results, as to what particular member of that group is
found. For the methods of making these determinations the
reader is referred to some book on bacteriology.*

Before proceeding with the laboratory test of a water, it is
essential to know something of the surroundings of the source
of supply. So long as the eye can re-enforce the other tests and
the whole course of the water may be clearly traced, it is com-
paratively easy to judge of the character of a supply and of its
safety for human use; but when a hole in the ground is the
visible source, or the actual history of the water is hidden in
unknown distances and depths, the diagnosis is more difficult.

The geological horizon and superficial soil must be studied;
the direction and flow of underground water, not the slope of the
surface only; the possible sources of danger, occasional as well
as constant, within at least a quarter of a mile radius. The
composition of unpolluted water of the same region should
always be at hand for consultation.

An examination of the environment is often sufficient to con-
demn a water, but cannot usually give it a clear certificate.
Laboratory tests should follow. In the next paragraphs will
be found a discussion of the interpretation of sanitary chemical
analyses.

Expression of Results. — Results of a sanitary chemical
analysis should be expressed in parts of any particular substance

* Prescott and Winslow, " Elements of Water Bacteriology." John Wiley &
Sons, New York, 1913.

SAFE WATER 59

per million of water. In most cases this is equivalent to milli-
grams per liter — the exceptions being where the water has an
appreciable specific gravity above i.o, such as sea water.

Accuracy of Methods. — In all water analyses very minute
quantities are sought after, and, therefore, all the tests applied
must be exceedingly delicate in character. The quantitative
results need not, however, be of great percentage accuracy.
For example, it makes no particular difference whether 0.050
or 0.055 parts of ammonia per million of water are found — an
error of 10 per cent. It might make a good deal of difference
if one found 0.2 of a part or 0.05 — a difference of 0.15 parts
per million, an amount which in most analytical work would be
entirely negligible. The American Public Health Association
has suggested that only a limited number of figures be used in
reporting an analysis, and thereby eliminate any impression of
false accuracy.

Above 10 parts per million. Use no decimals.

From I to 10 parts per million. Use i decimal.
From 0.1 to I part per million. Use 2 decimals.

In the determinations of ammonia and of nitrites 3 decimals
may be used.

The above discussion does not mean that the analyses should
be made in a careless or slipshod manner, in fact, quite the re-
verse is true, for there is no kind of chemical work which requires
greater care or cleanliness.

As little time as possible should elapse between the collection
and examination of samples of water. The more polluted the
water the more rapidly will changes take place, and, therefore,
all samples should be tested within 24 hours of their collection.
Samples for bacterial analysis should be examined immediately,
or if sent to a laboratory, should be packed in ice. Sewages and
sewage effluents should be analysed within six hours of collec-
tion, or if for chemical analysis should be chlorofonned (5 c.c.
per liter) to prevent chemical changes taking place.

Chemical Examinations. — The chemical analyses generally
made in sanitary work are the following: nitrogen as free am-

6o AIR, WATER, AND FOOD

monia, as albuminoid ammonia, as nitrates, and as nitrites;
chlorides in terms of chlorine; oxygen consumed; soap hard-
ness; total solids and loss on ignition; iron; and sometimes
oxygen dissolved. The interpretation of the results of each of
these will be discussed, and where possible, standard figures will
be given.

Nitrogen Cycle. — The most important determinations which
must be made in order to decide on the potability of the water
in question are those involving the nitrogen compounds and
chlorides. A clear understanding of the cycle of nitrogen in
nature is, therefore, necessary.

Nitrogen is present in living plants and animals mainly in
the form of organic compounds — the proteins and simpler
amino compounds. These substances, if boiled with alkaline
potassium permanganate, will give off part of the nitrogen in
the form of ammonia which can be collected and determined
quantitatively. This is called "albuminoid ammonia." When
the living plant or animal dies, the proteins are attacked by
bacteria and putrefy. In this process the nitrogen is converted
first into simpler amino bodies and finally into ammonium salts
or substances, such as urea, which readily yield ammonia. Thus,
the detemiinations of ammonia (called "free" ammonia) and
of albuminoid ammonia will indicate how far this putrefaction
has gone. A waste product, such as sewage, will give, when
fresh, both free and albuminoid ammonia in quantity, but on
standing, some of the organic nitrogen will change to ammonia,
so that the free ammonia will increase and the albuminoid am-
monia decrease. Thus, these analyses may be used to indicate
fresh or recent sewage pollution of a water supply.

When the organic nitrogen is largely converted to ammonium
compounds, and if oxygen is present, another kind of bacteria,
called the nitrosomonas, will act on the latter substances and
oxidize them to nitrites. This is the second stage in the nitrogen
cycle. Thus, the presence of nitrites in a water may indicate
less recent pollution than the presence of only free ammonia.

The nitrites, however, are not stable, and if sufficient oxygen

SAFE watp:r 6 1

is available, they are oxidized by still another set of micro-
organisms, the nitrobacter, giving nitrates. The nitrifying bac-
teria remained undiscovered for some time, owing to the fact
that they do not grow in the laboratory on any medium con-
taining large amounts of organic matter. Thus, the presence of
nitrates in a drinking water may indicate contact with sewage
at some past time, or as it is called, past pollution.

Nitrates are food for green plants, which in turn die or are
eaten by animals, the nitrogen being changed from the inor-
ganic back to the organic form, and the cycle thus completed.

But the cycle is not so simple as would appear. Nitrogen
may be lost from it in two w^ays. While ammonia is being oxi-
dized to nitrites, both may be present and interaction may
result with the formation of nitrogen gas.

NH3 + HNO2 -^ No 4- 2 H2O.

Or, nitrites may be reduced by micro-organisms with the liber-
ation of nitrogen. Nitrates may also be reduced to nitrites by
bacteria, iron, or possibly by organic matter.

Nitrogen may be added to the cycle as well as lost from it.
This takes place by means of the nitrogen-fixing bacteria which
occur largely in nodules on the roots of leguminous plants, such
as the clover, and also in some soils. These have the power of
removing nitrogen from the air and making it available for the
plant.

Practical use is made in the septic or Imhoff tanks of the
ability of micro-organisms to decompose organic matter and the
modern sewage filter is really a culture bed for the development
of nitrifying organisms w^hich act on the sewage and render it
stable by oxidizing the nitrogen compounds to nitrates.

As will be seen from the above discussion, a sanitary chemical
analysis depends primarily upon the determination of the con-
dition of the nitrogen compounds in a sample of water. Each
of these will be discussed separately.

Albuminoid Ammonia. — This is the ammonia which is set
free by the action of boiling alkaline potassium permanganate

62 AIR, WATER, AND FOOD

on nitrogenous organic matter. This may have entered the
water from perfectly harmless sources, such as dead vegetable
substances, or it may have come from waste material, such as
sewage. If from the former source, it is relatively stable and, if
present in any quantity, is accompanied by color in the water.
If from sewage, there may be little or no color, and the nitrog-
enous matter will be relatively unstable. The stability can be
determined by the action of the permanganate, stable substances
yielding ammonia only slowly and unstable substances losing it
rapidly.

The albuminoid ammonia gives no accurate measure of the
total nitrogenous organic matter present, as only about 50 per
cent is converted to ammonia, but it does give a good indica-
tion of whether or not the organic matter is easily decomposed,
and, therefore, whether or not it comes from sewage. A color-
less water should not contain over 0.15 parts per million of
nitrogen as albuminoid ammonia. The amounts found in good
ground waters are generally much lower than this figure.
Samples from storage reservoirs, in which there is plant life, may
contain larger amounts — up to 0.4 of a part.

The total organic nitrogen as determined by the Kjeldahl
method is sometimes used in place of the albuminoid ammonia,
but it gives no means of distinguishing between stable and un-
stable substances, and is not considered in this country to be as
good an index of pollution.

Free Ammonia. — This is the ammonia which comes off from
a water on direct distillation, the water being made alkaline if
necessary. The ammonia is probably present as ammonium
salts. Since this represents the first stage in the decomposition
of unstable nitrogenous organic matter, its presence in abnormal
quantities may be taken as an index of sewage pollution. The
amounts of ammonia present in good waters are generally very
small, and amounts over 0.15 to 0.2 parts expressed in terms of
nitrogen are sufficient to indicate pollution. In general, the free
ammonia is less than the albuminoid ammonia. If the reverse
is found it is an indication of trouble, unless both are very low.

SAFE WATER ' 63

Cases sometimes arise where abnormally high free ammonia
does not indicate sewage, and the analyst should continually be
on the lookout for these exceptions. One may be found in wells
dug in glacial drift, where ammonia may have come from fossil
remains. Another occurs sometimes when a well is located in
close proximity to an ammonia refrigerating plant.

Nitrites. — Nitrites in a water are formed either from the oxi-
dation of ammonia or the reduction of nitrates. In either case,
they represent an unstable condition, usually accompanied by
large numbers of bacteria, and in most cases sewage pollution
or surface contamination. As has been said, "a state of change
is a state of danger," and the presence of nitrites reveals this
condition. As has been mentioned, nitrites may be formed
from nitrates by reduction due to iron or organic matter, but
such cases are not at all usual.

A good drinking water should be either entirely free from
nitrites or should contain them only in very minute quantities.
Amounts of o.oi to 0.02 or more parts per million of nitrogen
are sufficient to condemn a water. But while the presence of
abnormal amounts of nitrites indicates danger, their absence is
no guarantee of the purity of a supply.

Nitrates. — As seen from the discussion of the nitrogen cycle,
nitrates are the fmal stage in the oxidation of nitrogen com-
pounds. Since they are food for plants, we would expect to
find only small amounts where there is any plant life. Thus,
surface waters are generally low in nitrates while ground waters
may be higher. It is probable that practically all nitrates in
waters have come originally from animal matter, as vegetable
nitrogen is not easily oxidized. In some cases, nitrates have
been known to come from chemical fertilizers used on fields.

High nitrates, combined with high chlorides, indicate past
pollution. "Past" is used either in the sense of time or dis-
tance. That is, fresh sewage may have found its way into a
well at some time past, and the nitrogen compounds may ha\-e
remained there, and 1)ccn oxidized until, at the time of examina-
tion, nitrates predominated over the other fomis. Or the sew-

64 AIR, WATER, AND FOOD

age may have come from such a distance that oxidation has
taken place in the passage through the ground.

The presence of high nitrates is not generally accompanied
by sewage bacteria, and, therefore, immediate danger from the
supply does not exist. The objection to using such waters for
drinking is, first, that if pollution has once entered, it may enter
again, and, second, that the natural filter through which the
water is passing may, at some time, fail to work properly and
allow sewage bacteria, and with them possibly typhoid organ-
isms, to enter the water. In other words, past pollution indi-
cates a condition of possible future danger, and it is safest to
avoid this either by not drinking such water or by watching it
carefully by means of frequent examination.

Good surface waters are low in nitrates, over i part of nitrogen
as nitrate per million of water being a suspicious sign. Ground
waters often run much higher than this even when unpolluted,
but above 5.0 parts, is in most cases, sufhcient to condemn the
water as unsafe for drinking.

Chlorides. — In interpreting the results of the analyses of the
various nitrogen compounds, it must be remembered that the
presence of any one of them in abnormal amounts is rarely
sufficient evidence upon which to declare a water unfit to drink.
The nitrogen compounds must be accompanied by an abnormal
amount of chlorides. Chlorides occur in w^aters principally as
the sodium salt, and as the results of analysis are generally ex-
pressed in terms of chlorine, this latter term is the one in common
use. Human urine contains about i per cent sodium chloride,
and the amount of sewage entering a well or stream can be ap-
proximately determined by the rise in the chlorine content.
Furthermore, chlorine passes through no such cycle as that of
nitrogen, and common salt is not taken up by most plants, so
that once in a water there is no way by which the chlorine can
entirely disappear. If, then, abnormal amounts of chlorine
accompanied by abnormal amounts of one of the nitrogen com-
pounds are found in a water, it is a pretty sure indication that
sewage, in some state, is entering.

STATE BOARD OF HEALTH

MAP OF THE

The lilies represent normal chlorine.

STATE OF MASSACHUSETTS. ^^SrortL.T"^ °'"°''°'' ""■* '

Q 'tf r^WTT TSif"* "^^ flRureB uoderlined rwppesenicliJorlnea of ground-

NORMAL CHLORINE.

SAFE WATER 65

The difficulty is to decide on what constitutes an abnormal
amount of chlorine, since salt occurs, to some extent, in most
soils and rocks, and in some places in very large quantities.
Some years ago, the Massachusetts State Board of Health at-
tempted to solve this problem by a careful study of a large
number of waters from all over the state. The chlorine was
determined in those which, from the surroundings and the other
constituents, could safely be regarded as free from pollution.
The figures obtained were placed on a map of the state at the
appropriate places and lines drawn through ecjual values. These
lines were termed "isochlors." This map is shown opposite.
(Note. The figures are given on the map in parts per 100,000.)
Since this map was made for Massachusetts, a number of other
states have made similar ones. The maps give with reasonable
accuracy the normal chlorine values for surface waters, but for
deep or artesian wells, the figures do not necessarily hold. Con-
sequently, in some states, for example in Illinois, it has been
found more satisfactory to give normal values according to the
source of the supply.

But the presence of chlorine in amounts above normal, alone,
is not sufficient to condemn a water. High chlorine and low
nitrogen are sometimes found together in a well water which
has been contaminated with wastes from a sink drain. The
ratio of nitrogen to chlorine can sometimes be used to distin-
guish between barn and human sewage, as the former contains
less chlorine than the latter for the same amount of nitrogen.
Excessively high nitrates with chlorine only slightly above
the normal sometimes indicates washings from a fertilized
field.

Mineral Matter. — Since water is a universal solvent, it is not
surprising to find considerable amounts of mineral matter under
the headings "total solids'' and "hardness." How much cal-
cium sulphate or magnesium chloride or other soluble mineral
matter is allowable in a potable water is for the physician rather
than the chemist to say, but it seems to be the consensus of
opinion that, for the normal healthy person, the presence of

66 AIR, WATER, AND FOOD

mineral matter, even in considerable quantities, is in no way
deleterious to the system.

As has been said, the human system possesses great adapta-
bility, not only for different foods, but for mineral substances
water-carried. Not so the steam-boiler or the laundry-tub,
which reacts very sensitively and affects the pockets of the
consumers. The determination of sulphates gives an indi-
cation as to how the hardness is divided, as permanent hard-
ness is caused principally by calcium sulphate.

In a region of soft water, high soUds with chlorine and nitrates
indicate sewage pollution. Silica is much more commonly
present, even in surface-waters, than is often supposed. What
its effect may be is unknown. Iron is not uncommonly found in
combination with organic matter in either surface or imperfectly
filtered waters in contact with soils poor in calcium salts. It is
frequently accompanied by free ammonia, which causes an
abundant growth of Crenothrix. It is also present in deep wells
in the form of bicarbonate, which precipitates on exposure to
warm air.

Organic Matter. — The amount of carbonaceous matter, de-
termined either by the oxygen-consumed test or by the loss on
igniting the soHds, is of little use in interpreting a water analysis;
it is too difficult to get concordant results. The latter test may
sometimes be of service in a qualitative way, because the residue
from a recently polluted water often gives a distinctive disa-
greeable odor when ignited. In some laboratories, the quan-
titative determination is omitted entirely.

Dissolved Oxygen. — During the last few years, the determina-
tion of the oxygen dissolved in water has assumed considerable
importance, because of the use of the test as an indication of
the sanitary condition of a harbor or river. As long as sufficient
oxygen is present, the putrefactive changes which give off dis-
agreeable odors will not take place. There is some difference of
opinion as to how low the oxygen content may be allowed to fall
and still prevent these changes, but 40 per cent of saturation is
a safe figure to use.

SAFE WATER 67

The test is also used to determine the putrescibiHty of a
sewage effluent as described later under that test. The object
is to determine the amount of oxygen absorbed by the organic
matter in the effluent.

Physical Tests. — These are of little importance as far as the
determination of pollution is concerned, but are generally in-
cluded in an examination in order to satisfy those who insist
that a water shall be attractive as well as safe.

Sewage Analysis. — Sewages may be tested to determine
their strength and constituents in order to help in deciding upon
the best method of treatment, and also as a basis for determin-
ing the amount of purification which any process gives. The
analysis of effluents is carried on also for this latter purpose, and
in order to determine their putrescibiHty. For an extended
discussion the reader is referred to another book.*

Value of Tests. — It is often asked if some tests cannot be
made by the ordinary person of average intelligence which
will enable him to tell the quality of a water as well as the
expert to whom he pays ten or twenty dollars for an opinion.
A careful perusal of the preceding pages will have answered
the question in the negative. There is no assay of water as
there is of gold and silver. Not one, but ten or twenty tests
must be made. Not only must the tests be made with the
utmost care and cleanliness of person, utensils, and room, but
the results must be studied in the light of other experience and
other knowledge, geological and biological, and after all this is
done, there is an array of circumstantial evidence which must
be carefully weighed by one whose judgment and experience
enable him to read clearly where another might see nothing.
The value of a water-analysis is in direct proportion to the
knowledge and experience of the one who interprets it. Clinical
skill in addition to theoretical knowledge is as much required
to interpret the figures obtained in the course of a water-analy-
sis, as in the diagnosis of a disease; and the analog}^ goes still
further, for just as some diseases are clearly defined, and others
* Fowler, '' Sewage Works .\nalysis."

68 AIR, WATER, AND FOOD

are so complicated that only those who have had long experience
can outline a safe course of treatment, so some waters bear the
marks of their character so plainly as not to admit of mistake,
while others require most careful study. For these reasons, the
value of water-analysis should not be decried because the fears
aroused by reports given by unskilled analysts prove ground-
less, any more than the practice of medicine should be discarded
because inexperienced men make mistakes.

Is the water in any given case safe for drinking? To answer
this question there is needed a knowledge, wider than a chem-
ist's, of the relation of decaying organic matter and of the
germ-carrying power of water to outbreaks of disease. There
must be added the knowledge of the biologist, the engineer,
and the sanitarian.

CHAPTER VI

WATER : ANALYTICAL METHODS *

Water-analysis cannot be carried on in an ordinary labora-
tory. In order to obtain satisfactory results, it is necessary to
have a room set apart for the purpose, and to exclude rigidly all
operations which tend to the production of fumes or dust.
Where such minute traces of substances are dealt with as in
water-analysis, too much care cannot be taken to insure the
absolute cleanliness of the apparatus and the surroundings. It
is desirable that the room be well lighted, and, if possible, the
windows should face toward the north.

For the collection of water samples, glass-stoppered bottles of
about a gallon capacity are best. Those used in this laboratory
are of white glass, 15 inches high to the top of the stopper, five
and a half inches in diameter, and weigh about three pounds.
They have flat, mushroom stoppers, on each of which is engraved
a number to correspond with that on the bottle. The bottles,
before being sent out, are thoroughly cleaned with potassium
bichromate and sulphuric acid, washed with distilled w^ater and
dried. If glass-stoppered bottles are not at hand, new demi-
johns fitted with new corks may be used. A glass bottle or a
demijohn is much to be preferred to an earthenware jug, because,
if for no other reason, it is so much easier to be sure that the
interior is clean. It should always be borne in mind that in
water-analysis the question is one of very minute quantities of
material, and that the methods to be employed are extremely
deHcate. Hence, in the case of many waters, careless handling
of the sample would contaminate the water to a sufficient ex-
tent to render valueless the results obtained in the laboratory.

* See " Standard Methods for the Examination of Water and Sewage," Ameri-
can Public Health Association, 1912.

70 AIR, WATER, AND FOOD

In collecting samples, the following directions should be closely
followed:*

Directions for Collecting Samples for Analysis. — From a
Water-tap. — Let the water run freely from the tap for a few
minutes before collecting the sample. Then place the bottle
directly under the tap and rinse it out with the water three
times, pouring out the water completely each time. Place it
again under the tap; fill it to overflowing and pour out a small
quantity so that there shall be left an air-space under the stopper
of about an inch. Rinse off the stopper with flowing water;
put it into the bottle while still wet and secure it by tying over
it a clean piece of cotton cloth. Seal the ends of the string on
the top of the stopper. Under no circumstances touch the in-
side of the neck of the bottle or the stem of the stopper with
the hand, or wipe it with a cloth.

From a Stream, Pond, or Reservoir. — Rinse the bottle and
stopper with the water, if this can be done without stirring up
the sediment on the bottom. Then sink the bottle, with the
stopper in place, entirely beneath the surface of the water and
take out the stopper at a distance of twelve inches or more be-
low the surface. When the bottle is full replace the stopper,
below the surface if possible, and secure it as directed above.
It will be found convenient, in taking samples in this way, to
have the bottle w^eighted so that it will sink below the surface,
and to remove the stopper with a cord. It is important that the
sample should be obtained free from the sediment at the bottom
of a stream and from the scum on the surface. If a stream
should not be deep enough to admit of this method of taking a
sample, dip up the water with an absolutely clean vessel and
pour it into the bottle after the latter has been rinsed.

The sample of water should be collected immediately before
shipping by express, so that as little time as possible shall inter-
vene between the collection of the sample and its examination.
All possible information should be furnished concerning the
source of the water and of possible sources of contamination.
* Ann. Re pi. Mass. State Board of Health, 1890, p. 520.

WATER: ANALYTICAL METHODS 7 1

For example, in the case of a well, the proximity of dwellings,
cesspools, or drains should be recorded, and the character and
slope of the soil, whether toward or away from the well, should
be noted. In the case of a surface-water, mention any ab-
normal or unusual conditions; as, for instance, if the streams
or ponds are swollen by recent heavy rains, or are unusually low
in consequence of prolonged drought, or if there be a great deal
of vegetable growth in or on the surface of the water. Record,
in short, any circumstantial evidence which by any possibility
may aid in the final judgment.

TJie question of proper collection of samples is an important one,
and the chemist is perfectly justified in refusing to give an opinion
in regard to the purity of a water which he has not himself collected.

Preparation for Analysis. — Since changes in the composition
of a contaminated water are constantly going on, the analysis of
the sample should be begun without delay. The bottle is held
under the tap, and the neck and stopper are washed free from
adhering dust. The stopper is rinsed off with some of the water
from the bottle.

If the sample has stood for several hours, allowing suspended
matter to settle, the conditions of turbidity and sediment, as de-
scribed on page 108, may first be observed. The sample is then
thoroughly mixed and qualitative tests made for alkalinity,
ammonia and chlorides. Make the alkalinity test with methyl
orange indicator. If a sample is acid, it is necessary to make
alkaHne, as described later, before starting the determinations
for free ammonia and chlorides. IMake the test for ammonia
by adding two c.c. of Nessler reagent to 50 c.c. of the sample in
a Nessler tube. A reddish-brown color or precipitate means the
presence of large amounts of ammonia, and care should be taken
not to take too much of the sample for the quantitative deter-
mination (see page 74). A qualitative test for chlorides will
determine the amount of water to be taken for the analysis, —
a very slight opalescence meaning low chlorides, which will
necessitate the use of a 250-c.c. sample, while a distinct tur-
bidity or a precipitate will allow a 25-c.c. sample to be used.

72 AIR. WATER, AND FOOD

As the nitrogen compounds are more subject to important
changes than any others, it is desirable to make these determi-
nations first, the order of the remainder being immaterial.

It is essential that the sample of water be thoroughly mixed
each time any is withdrawn, as only in this way will the samples
removed be of constant composition. This is particularly im-
portant in dealing with sewages and sewage effluents, or where
there is a considerable amount of suspended matter.

The methods for preparing standard solutions and other
special reagents will be found in Appendix B.

Determinations of Free and Albuminoid Ammonia. — Am-
monia occurs in waters as ammonium salts, — carbonate, chlo-
ride, or nitrate. In sewages it may be partially present as the
hydroxide. On boiling an alkaline solution of these substances,
the salts are decomposed, as well as some unstable organic com-
pounds such as urea, and ammonia passes off and dissolves in
the condensed steam. The ammonia thus collected is called the
"free ammonia." If, now, alkaline potassium permanganate is
added to the water left after the free ammonia has been removed,
and the boiling continued, part of the nitrogenous organic mat-
ter will be decomposed with the liberation of ammonia. This
is termed " albuminoid ammonia."

The principles involved in the two determinations have been
described in the above definitions, that is, the water is first
boiled, and the steam condensed until all the free ammonia
has been removed. Then alkaline potassium permanganate is
added, and distillation continued until no more albuminoid
ammonia is evolved. The ammonia is determined in the dis-
tillates by means of Nessler reagent which gives a greenish
yellow with very small amounts of ammonia, and yellow to red-
dish brown with larger quantities. The exact amount of am-
monia is obtained by comparison of the colors obtained with
those from known amounts of ammonia.

Nessler reagent is a solution of potassium mercuric iodide
(K2Hgl4) containing potassium hydroxide. The colored sub-
stance formed when this reacts with ammonia is dimercuram-

WATER: ANALYTICAL METHODS

monium iodide (NHg2l • H2O), which is an ammonium iodide in
which the hydrogen atoms have been substituted by mercury.
This substance is sHghtly soluble in an excess of potassium iodide
and potassium hydroxide, giving a color proportional to the
amount of ammonia present.

Apparatus and Reagents. — The apparatus consists of a
750 c.c. round-bottomed flask, having square shoulders and a
narrow neck five inches long, and an ordinary Liebig con-

FiG. 8.

denser fitted with a block-tin inner tube -f^ of an inch in diam-
eter which extends just through a cork stopper closing the
flask. The apparatus is set so that the distillate may be col-
lected directly in a 50 c.c. Nessler tube. The flasks are heated
either with the free flame of a Bunsen burner or with an electric
flask heater. These latter are somewhat slow in heating up
and in cooling, but give an even heat with just about the proper
rate of distillation and show little tendency to cause " bump-
ing." In place of the Liebig condenser, the tin tube may be
passed through a copper or galvanized iron tank (see Fig. 8),

74 AIR, WATER, AND FOOD

fitted with proper inlets and outlets, and serving as a con-
denser for a number of flasks. New flasks are treated with
boiling dilute sulphuric acid and potassium bichromate before
they are used. New corks should be steamed out for one or
two hours. A good sound cork will last for several months
with daily use.

The Nessler tubes used should be of the same height up to
the 50 c.c. mark.

Reagents necessary are Nessler solution, alkaline potassium
peniianganate, a standard ammonium chloride solution and
ammonia-free water (see Appendix B).

Procedure. — Free the apparatus from ammonia by placing
500 c.c. of ammonia-free water in the flask and distilling. Col-
lect the distillate in 50 c.c. Nessler tubes, and test each tube as
it is filled, by adding two c.c. of Nessler reagent and comparing
the color obtained after waiting five minutes with that obtained
by adding two c.c. of Nessler reagent to 50 c.c. of ammonia-free
water. This latter gives a zero standard. Continue until the
distillate is free from ammonia and then pour the water left in
the flask into the bottle marked " ammonia-free residues."

While this is going on make a qualitative test on the sample
of water to determine the amount which should be used for the
quantitative determination. To do this, add to 100 c.c. of the
water, removed from the bottle only after thorough mixing,
one c.c. of 10 per cent copper sulphate solution, and one c.c. of
50 per cent potassium hydroxide. Allow to settle and filter
through a dry paper into a 50 c.c. Nessler tube, discarding the
first 10 c.c. of filtrate. Add two c.c. of Nessler reagent, and
allow to stand for 10 minutes. Make a standard by placing
two c.c. of the standard ammonium chloride solution in a Nessler
tube, making up to 50 c.c. with ammonia-free water, mixing
thoroughly and adding two c.c. of Nessler reagent. If the color
obtained from the sample of water is less than this standard,
use a 500 c.c. sample of the water for the determination; if
equal to or greater than the standard, use a 100 c.c. sample;
if the color is so deep that a precipitate forms, use a lo-c.c.

WATER: ANALYTICAL METHODS 75

sample. For sewages five or 10 c.c. are sufficient. In case less
than 500 c.c. are used, dilute the amount to this volume with
ammonia-free water.

Test some of the water with methyl orange for acidity. If
acid, 0.5 gram of pure sodium carbonate must be added before
starting the distillation. The great majority of drinking waters
are alkaline, but once in a while an acid water turns up, and it
is well to be on the lookout. Acid sewages and sewage filter
effluents are not uncommon.

When the apparatus has been freed from ammonia, shake
thoroughly the bottle containing the water sample, and measure
out in a calibrated flask 500 c.c, or a smaller amount, according
to the quahtative test described above, adding enough ammonia-
free water to make the total volume at least 500 c.c, and
pour into the distilling flask. If necessary, add sodium car-
bonate. Distill three portions of 50 c.c. each into well-rinsed
Nessler tubes. Regulate the height of the flame so that the
time of distilling 50 c.c. shall not be more than eight and not
less than five minutes. In most cases three portions are suffi-
cient to collect all the free ammonia, but it is well to test the
last portion with Nessler reagent, and compare it with a zero
ammonia standard, before proceeding further. Save these por-
tions for nesslerization, as they contain all the free ammonia.

After the free ammonia has been distilled off, allow the con-
tents of the flask to cool for 10 minutes; then add 40 c.c. of
alkaline pennanganate through a funnel, taking care that none
of the alkahne solution touches the neck of the flask, and pro-
ceed with the distillation of the albuminoid ammonia. With
colored waters distill off five portions of 50 c.c. each; with
colorless waters, three or four portions will suffice. These
portions contain the albuminoid ammonia.

Unless permanent standards are used, prepare standards by
adding to Nessler tubes nearly filled with ammonia-free water
varying quantities of the standard ammonium chloride solution ;
for instance, o.i, 0.3, 0.5, 0.7, i.o, 1.3, 1.5, 2.0, 2.5, 4.0, 6.0 c.c
The standard ammonium chloride solution contains 0.0000 1 2;ram

AIR, WATER, AND FOOD

N in one cubic centimeter. Mix the contents of the tubes by ro-
tating them between the palms of the hands or by pouring into
another Nessler tube and back again (never shake them Hke a
test-tube or stir them with a rod), allow them to stand for a few
minutes and add two c.c. of Nessler reagent to each tube and
to each of the portions of distillate. At the end of lo minutes
match the colors and record the amount of ammonia in terms
of cubic centimeters of the standard ammonium chloride solu-
tion. From the value of this solution calculate the amounts of
free and albuminoid ammonia as parts of nitrogen per million
of water.

As an example, the following results from distilling 500 c.c.
may be given.

Free ammonia.

Albuminoid Ammonia.

ist 50 C.C.
2nd 50 C.C.
3d 50 C.C.

, 0.7 CC.

0.3 C.c

, 0.0 C.c.

ist 50 C.C, 4.5 C.C.
2nd 50 c.c, 2.8 c.c.
3d 50 c.c, 1.5 c.c.
4th 50 c.c, 1 .0 c.c.
5th 50 c.c, 0.5 c.c

i.o c.c.

10.3 c.c.

In this case, the free ammonia would be 0.020 and the albumi-
noid ammonia 0.206 parts per million.

In dealing with sewages or sewage effluents, which are very
high in free ammonia, if the ammonia were collected in three
portions, so much would distill over in the first portion that the
color given with the Nessler reagent would often be too deep to
read or a precipitate might form. To avoid this, the total dis-
tillate of 150 to 175 c.c. is collected in a 200-c.c. graduated flask,
made up to the mark, thoroughly mixed by pouring into a clean
dry beaker and back again, and then 50 c.c. of it taken for
nesslerization. In this way, the ammonia is distributed more
evenly in the distillate and the determination is not sacrificed.

If free ammonia only is desired in a sewage or sewage effluent,
a direct determination is to be preferred over distfllation. For

WATER: ANALYTICAL METHODS 77

this, proceed as directed in the c^ualitative test for ammonia, ex-
cept that a smaller amount of the filtrate should be used, two
or five c.c, and this made up to 50 c.c. with ammonia-free water,
treated with Nessler reagent, and matched against standards
as just described.

Notes. — Where a large number of determinations are made
at frequent intervals, permanent Nessler standards are a great
convenience. These should be made according to directions
found in " Standard Methods,"* but should be adjusted by
comparison with nesslerized standards made from ammonium
chloride solution.

It is impossible to convert all of the organic nitrogen into
ammonia by boiling with alkaline permanganate. The amount
of ammonia which is thus obtained depends not only upon the
character of the substances, but also upon the concentration of
the solution and the rate of boiling. In order that the albu-
minoid ammonia in potable waters shall bear some definite
relation to the total organic nitrogen, it is necessary that
conditions shall be duplicated as nearly as possible in differ-
ent determinations; that is, the alkaline permanganate must be
added to a definite volume of water, and the boiling must be
carried on at a definite rate. Some of the highly-colored surface-
waters give up their nitrogen very slowly by this treatment;
polluted waters, on the other hand, yield the ammonia more
rapidly, so that the observation of the relative amounts found
in the successive portions is of the utmost importance in form-
ing a judgment.

A depth of color given by six c.c. pf the standard ammonium
chloride with the Nessler reagent is about the limit of satisfactory
comparison in the ii-inch 50 c.c. tubes. The color given by
10 or 12 c.c. of the standard may be matched in the 100 c.c. tubes
with a depth of five inches and a diameter of i^ inches.

For most cases, where great exactness is not essential, it is
possible to divide the 50 c.c. or the 100 c.c. portion into two

* "Standard Methods of Water .\nalysis," American Public Health .\sso-
ciation, 1912, p. 17.

78 AIR, WATER, AND FOOD

equal parts by pouring into a tube the exact counterpart of the
standard tube and matching the color. It is even possible to
approximate closely the correct result by the use of a foot rule.
The standard is, we will assume, five c.c. The height of the
liquid in the tube to be tested we will call nine inches. If the
height of the column left which matches five c.c. is three inches,
then the reading was 15 c.c. of the standard.

The limit of solubility of the mercur-ammonium iodide is
reached at 25 or 30 c.c. of the standard in 50 c.c. The incipient
precipitate not only changes the color of the solution, but causes
a slight milkiness or turbidity which prevents a sharp reading
of the color.

The test is an excellent example of quantitative color work
when carried out under strictly comparable conditions.

It should, perhaps, be stated that in both the ammonium and
nitrate determinations, as also in that of iron, dilution of the
sample in which the color is already developed does not give a
correct result. Therefore dilution, if necessary, must be made
before the reagents are added.

In order to secure the most accurate results, it is important
that the temperature of the distillates to be nesslerized and of
the standards be the same, since the warmer solutions give a
more intense color with the Nessler reagent.

Total Organic Nitrogen, Kjeldahl Process. — The principles
involved in the method consist in the oxidation of the carbon
and hydrogen of the organic matter with boiling sulphuric acid,
the nitrogen being converted into ammonia and held by the acid
as ammonium sulphate. The ammonia is then liberated and
distilled off from an alkaline solution.

Apparatus and Reagents. — The apparatus used is that shown
in Fig. 9. This is an arrangement for distilling with steam.
The reagents needed are nitrogen-free sulphuric acid and potas-
sium hydroxide (see Appendix B).

Procedure. — Measure 500 c.c. of the water into a round-
bottomed flask of 750 c.c. capacity and boil until about 200 c.c.
have been driven off. (The free ammonia which is thus ex-

WATER: ANALYTICAL METHODS

pelled may be determined, if desired, by connecting the flask
with a condenser.) Allow the water remaining in the flask to
cool, and add lo c.c. of pure concentrated sulphuric acid free
from nitrogen. Mix by shaking;
place the flask in an inclined posi-
tion on wire gauze under the hood
and boil cautiously until the water
is all driven oft". Place a small
funnel in the neck of the flask to
prevent the escape of acid fumes,
and continue the heating for at
least half an hour after the sul-
phuric acid becomes white. Mean-
while, rinse out the distilling ap-
paratus and free it from ammonia
as usual. Then, after the acid in
the digestion flask has cooled, rinse
down the neck of the flask with
loo c.c. of ammonia-free water and
attach the flask to the distillation
apparatus. Add loo c.c. of potas-
sium hydroxide solution through
the separatory funnel and distill
off the ammonia with steam, re-
ceiving the distillate in a 250-c.c. graduated flask. Conduct
the distillation rather slowly until the first 50 c.c. have distilled
over, then distill more rapidly until about 175 c.c. have been
collected. Make the volume of the distillate up to 250 c.c.
with ammonia-free water, mix it thoroughly and take 50 c.c.
for nesslerization.

The use of mercury and of potassium permanganate to assist
in the oxidation has been found to be unnecessary, as the organic
matter in natural waters is much more easily oxidized than in
other substances, — flour, for instance. The presence of nitrates
and nitrites in waters has not been found to interfere with the
accurate determination of the organic nitrogen. The error,

Fig.

8o AIR, WATER, AND FOOD

which has been found by Kjeldahl and Warrington to be caused
by the presence of nitrates seems to disappear when the organic
material is diluted to the considerable extent that exists in
natural waters. The high chlorine found in some well-waters
does not interfere with the method to any extent, but this de-
termination does not possess much value in this class of waters,
which are low in organic nitrogen.

In carrying out the digestion with sulphuric acid, the greatest
care must be taken to prevent access of ammonia or dust from
any source. The acid solutions will absorb ammonia from the
air or from the dust of the laboratory if they are allowed to re-
main uncovered for any length of time. This source of error
may in some instances be sufhciently large to render a determi-
nation valueless, even in a room which is, to all appearances, free
from ammonia-fumes. Hence, the operation should, if possible,
be carried to completion within twenty-four hours, and for every
set of determinations a blank analysis should be made with am-
monia-free water in order to make a correction for the ammonia
in the reagents, and for that accidentally introduced during the
process.

As the result of many hundred comparative determinations
of the organic nitrogen and of the albuminoid ammonia in nat-
ural waters which take their origin in the glacial drift, it has
been found that the nitrogen given by the albuminoid-ammonia
process, as directed in the previous pages, is about one-half of the
total organic nitrogen as given by the Kjeldahl process; in the
case of sewages and polluted waters, it is very variable owing to
their irregular composition.

Determination of Nitrogen in the Form of Nitrites. — This de-
termination depends on the formation of a pink azo dye by the
interaction of sulphanilic acid, naphthylamine acetate, and nitrous
acid. If an excess of the first two reagents is used, the amount
of dye and, therefore, the depth of color will be proportional to
the amount of nitrite present in the water. The color is then
compared with a series of standards made from a sodium nitrite
solution of known strength and the nitrite computed in terms of
nitrogen.

WATER: ANALYTICAL METHODS 8l

The reactions which take place are, first, the diazotizing of the
sulphanilic acid by the nitrous acid present, and then the inter-
action of this diazo compound with naphthylamine to form the
colored substance, a-naphthylamine-para-azo-benzene-para-sul-
phonic acid.

/NH2
C6H4 + C10H7NH2 + HNO2 ->

'^SOsH

/ N = N ^
CioHe^ C6H4 + 2H2O.

^ NHo SO3H ^

Apparatus and Reagents. — The only special apparatus needed
is a number of 100 c.c. Nessler tubes. The reagents used are a
standard sodium nitrite solution (i c.c. contains o.ooooooi
gram nitrogen), a solution of sulphanilic acid in acetic acid, a
solution of naphthylamine acetate, and a suspension of alumi-
num hydroxide (see Appendix B).

Procedure. — If the water is colorless, measure out 100 c.c.
into a loo-c.c. Nessler tube. If the water possesses color which
cannot be removed by simple filtration, it should be decolorized
as follows: Thoroughly rinse with the water a 250-c.c. glass-
stoppered bottle; pour into it about 200 c.c. of the sample,
add about three c.c. of milk of alumina and shake the bottle vig-
orously. Let stand for 10 or 15 minutes and filter through a
small plaited filter which has been thoroughly washed with
water free from nitrites. To 100 c.c. of the filtered sample or of
the originally colorless water add 10 c.c. of the sulphanilic acid
in acetic acid and 10 c.c. of naphthylamine acetate solution.
A pink color shows the presence of nitrite. To detennine the
amount* of nitrite present make up standards by placing 5 c.c,
10 c.c, 15 c.c, and 20 c.c. each of the standard nitrite solution
in loo-c.c Nessler tubes. Make up to 100 c.c. with nitrite-free
water, mix by pouring into a Nessler tube and back to the original
tube, and then add the reagents as before. Allow to stand 10

* Standard color papers and also acid solutions of fuchsine are used for nitrite
standards. Neither of these has been found very satisfactory in this laboratory.

82 AIR, WATER, AND FOOD

minutes, and match with the color obtained from the water
sample. If this does not match any of the standard colors,
make up intermediate standards. Do not attempt to match
colors closer than to one c.c. of the nitrite solution. If the
color is deeper than that given by 20 c.c. of the standard nitrite
solution, start a new determination using a smaller quantity of
water and diluting to 100 c.c. with the ammonia-free water.

One c.c. of the standard nitrite solution equals o.ooooooi
gram nitrogen. Determine the number of c.c. needed to match
the color obtained from the water sample and calculate the
results in parts of nitrogen per million of water.

Notes. — In case the color obtained is deeper than 20 c.c. of
the standard, an aliquot part may be measured, as described
under the ammonia determination. This. will be sufficiently
accurate for most purposes.

When once obtained, the color will remain unchanged for one-
hah to three-quarters of an hour. If left for a longer time, the
nitrites absorbed from the air will noticeably increase the color.

Determination of Nitrogen in the Form of Nitrates.* — This
determination depends on the action of nitric acid on phenol-
disulphonic to form nitrophenoldisulphonic acid, which gives
an intensely yellow color in alkaline solution. The reactions
involved can be expressed as follows:

/OH
CeHs - SO3H + HNO3 -^ C6H2 < gQ^g + H2O

\n02

\SO3H
.OH

SO3H

OK
SO3K

'-'^^^^ SO3H+ 3 KOH -> CeHo < l)?^ + 3 H2O

Reagents. — The reagents needed are a standard nitrate solu-
tion of which one c.c. contains o.oooooi gram nitrogen, and phe-

* Sprengel, Fogg, Ann., 1863, 121, p. 188; Grandval and Lajoux, Compt. rend.,
1865, loi, p. 62; Gill, J. Am. Chem. Soc, 1894, 16, p. 122; Chamot & Pratt, /.
Am. Chem. Soc, 1909, 31, p. 922; 1910, 32, p. 630; Chamot, Pratt and Redfield,
/. Am. Chem. Soc, 1911, 33, p. 366.

WATER: ANALYTICAL METHODS 83

noldisulphonic acid (see Appendix B). Care should be taken
in making this latter reagent as the results are dependent upon
its composition.

Procedure. — For ground waters, measure with a pipette two
samples of the water, one of two c.c. and the other of five c.c,
into three-inch porcelain evaporating dishes and evaporate just
to dryness on the steam bath or electric plate run at low heat.
For surface-waters use 10 c.c. If the water is colored, decolor-
ize with alumina as described under nitrites. Do not allow the
residue to remain on the steam bath after all the water has been
evaporated. Cool, add six drops of phenoldisulphonic acid and
rub with a glass rod to insure complete contact of the acid and
residue. Then add seven c.c. of distilled water and three c.c. of
30 per cent potassium hydroxide solution and mix thoroughly. A
yellow color shows the presence of nitrates. Place this solution
in a short Nessler tube* for comparison with a standard. This
standard is prepared as follows: Place one c.c. of potassium hy-
droxide solution in a short Nessler tube and add standard nitrate
solution from a burette until the color of the standard nearly
matches that of the water sample. Make the volumes of the
two solutions equal by diluting the standard and then add more
standard nitrate solution until the colors exactly match. Use
the sample of water for comparison which has the lighter color,
unless there is no yellow at all. In case the five c.c. sample
gives no color, repeat the determination, using 10 c.c. If this
gives no color nitrates are absent. If the two c.c. sample gives
a color which requires more than 10 c.c. of the standard, repeat
the determination, using smaller amounts of water.

The standard nitrate solution contains 0.00000 1 gram N per
c.c. From the amounts of standard nitrate solution and of
water used calculate the amount of nitrate present expressed as
nitrogen in parts per million of water.

Notes. — High chlorides seriously affect the accuracy of the
method. This is noticeable in dealing with sea water and deep
wells which contain large amounts of sodium chloride. In this
* An ordinar>- 50-c.c. Nessler tube cut off to a length of about five inches.

84 AIR, WATER, AND FOOD

case, the reduction method with alkali and aluminum foil and
distillation of the ammonia formed, is to be recommended.* For
most drinking waters it is not necessary to use this method,
which requires a much longer time than that described above.

Determination of Chlorine. — Chlorine is present in waters
in the form of chlorides, and the term "chlorine" is used to
mean " chlorides " as the results of analysis are given in terms
of chlorine.

The determination is made by titration with silver nitrate in
a solution alkahne with bicarbonates, — the condition generally
existing in natural w'aters, — potassium chromate being used as
an indicator.

Reagents. — The solutions required are a standard sodium
chloride solution (i c.c. contains o.ooi gram CI), a solution of
silver nitrate about one-half as strong, and potassium chromate
indicator (see Appendix B).

Procedure. — Standardize the silver nitrate solution b}^ ti-
trating against a standard sodium chloride solution. To do this
place 25 c.c. of distilled water in a 6-inch porcelain evaporating
dish, add three drops of potassium chromate indicator, and then
run in from a burette a measured amount of sodium chloride
solution, about live c.c. being sufficient. It is not necessary to
add exactly five c.c, but it is necessary to know the exact amount
added. Now add silver nitrate solution from a burette until
the yellow color of the solution has changed to a faint reddish
brown. The end point is best seen if 25 c.c. of distilled water
and three drops of indicator are placed in a 6-inch dish which
is set beside the dish in which the titration is being carried on.
This gives a standard color and the end point is reached when
the solution being titrated shows the slightest appearance of
red as compared with the standard. From the results of the
standardization calculate the value of silver nitrate solution in
terms of sodium chloride solution and in terms of CI per c.c.

Test the water to be analyzed with phenolphthalein and with
methyl orange. It should be acid to the former and alkaline

* See "Standard Methods," p. 25.

WATER: ANALYTICAL METHODS 85

to the latter. If alkaline to phenolphthalein neutralize the
sample measured for titration with dilute sulphuric acid. If
acid to methyl orange neutralize with sodium bicarbonate.

Highly colored waters should be decolorized before titration
as the color interferes with the end point. To do this shake
some of the sample in an Erlenmeyer flask with milk of alu-
mina, one c.c. of the latter being used for each 100 c.c. of water.
Heat the mixture rapidly to boiling, allow to settle and decant
through a filter.

Make a qualitative test for chlorides on the sample of water.
If only a faint opalescence appears, a 250 c.c. sample must be
used for analysis; if a marked cloudiness or a precipitate is
formed, a 25 c.c. sample may be used. If the larger sample is
found to be necessary, evaporate to about 25 c.c. on a steam
bath or electric plate; avoid boiling. Cool before titrating.

To 25 c.c. of the water, measured wdth a pipette, or an evap-
orated 250 c.c. sample, in a 6-inch porcelain dish, add three drops
of indicator and about five c.c. of sodium chloride solution, the
exact amount being measured as in the standardization. Then
run in silver nitrate solution until the end point is reached,
using the standard color as before.

From the amounts of silver nitrate and sodium chloride solu-
tions used calculate the amount of chlorine present in parts per
million.

Notes. — With waters containing large amounts of chlorides,
the addition of sodium chloride in the titration may be omitted.

It is important that the process be carried out essentially as
described, since it has been found that the results vary with
the volume of solution in which the titration is made, the amount
of chromate used, and the amount of precipitated chloride pres-
ent.*

Determination of the Carbonaceous Matter or " Oxygen
Consumed." — This determination is supposed to give the
amount of oxygen absorbed by the organic matter present in
the water. Except in sewage analysis, the results are of little

* Hazen, Am. Chem. J ., 1889, 11, p. 409.

86 AIR, WATER, AND FOOD

importance, and the determination may be omitted without
appreciably aflfecting the interpretation of the results of the
whole analysis.

The oxygen consumed is determined by allowing an excess
of potassium permanganate in acid solution to act on the or-
ganic matter in the water under certain conditions, and then
titrating the excess of permanganate with ammonium oxalate.
Equations:
4 KMn04 + 6 H2SO4 + 5 C -^ 2 K2SO4 + 4 MnS04 + 6 H2O

+ 5 CO,.
2 KMn04 + 3 H2SO4 + 5 C2H2O4 . 2 H2O -^ K2SO4 + 2 MnS04
+ 10CO2 + 18H2O.

Reagents. — The solutions required are a standard ammo-
nium oxalate solution (i c.c. equals o.oooi gram oxygen), a
potassium permanganate solution of approximately the same
strength, and 1-3 sulphuric acid (see Appendix B).

Procedure. KuheVs Hot Acid Method. — Standardize the
potassium permanganate against the oxalate in the following
way: Measure 100 c.c. of distilled water into a 250-c.c. flat-
bottomed flask, add 10 c.c. of sulphuric acid (1-3) and then add
from a burette a measured quantity (about 10 c.c.) of standard-
ized potassium permanganate solution. Place the flask on a
wire gauze or electric stove and heat quickly to boiling. Boil
the solution gently for exactly five minutes, remove it from the
flame, cool for one minute, and add from a burette sufficient
ammonium oxalate to decolorize the solution. Titrate back
with the permanganate to a faint permanent pink color. Cal-
culate the value of the permanganate in terms of standard
ammonium oxalate and of oxygen.

For the analysis proceed just as in the standardization, re-
placing the distilled water by the sample to be tested. The
oxygen consumed value for the water under examination is
obtained from the number of c.c. of permanganate used in
excess of that required to react with the oxalate added in the
determination. Calculate the results in parts of oxygen per
million of water.

WATER: ANALYTICAL METHODS 87

Notes. ■ — For highly colored surface-waters 25 c.c. are taken
and diluted to 100 c.c. with w-ater free from organic matter; for
sewages, 10 c.c. or less are diluted in the same way.

The oxygen given up by the permanganate combines with the
carbon of the organic matter and perhaps, to a certain extent,
with the hydrogen, but not with the nitrogen. The amount of
oxygen consumed bears some relation, therefore, to the amount
of organic carbon present in the water, but this relation cer-
tainly cannot be taken as a definite one in every case, the results
varying even with the time of boihng. The method has its
greatest value when it is used to compare waters of the same
general character and having the same origin; for example, in
making periodical tests of the purity of the effluent from a filter.
Furthennore, in order that the results shall have this compara-
tive value, it is absolutely necessary that the process shall
always be carried out in exactly the saine way, even to the
minutest detail of quantity, time and temperature.

In some cases it may be found advantageous to heat the solu-
tion upon the water-bath for half an hour instead of boiling it
for five minutes. The results, however, will not be exactly
comparable with those obtained by boiling.

Different kinds of organic matter behave differently with
various oxidizing agents, so that a comparison of the results
obtained with different oxidizing agents may throw light upon
the character of the organic matter, as w^ell as its amount.*
In waters from the watersheds of eastern North America the
color and the oxygen consumed have a certain, though some-
what varying, relation.

Determination of the Residue on Evaporation and the Loss
on Ignition. — Procedure. — Carefully clean a large platinum
dish, ignite for a few minutes over a burner, cool in a desiccator
and weigh. Measure into it 100 c.c. of the water (200 c.c. in
the case of surface-waters), and evaporate to dryness on the
water-bath. WTien the water is all evaporated, heat the dish
in the oven at the temperature of boiling water for one hour,
* Woodman, /. Am. Client. Soc, 189S, 20, p. 497.

88 AIR, WATER, AND FOOD

cool in a desiccator over sulphuric acid, and weigh. The increase
in weight gives the 'Hotal solids" or "residue on evaporation."

The residue should be ignited and the loss on ignition noted.
Heat the dish in a "radiator," which consists of another plat-
inum dish enough larger to allow an air-space of about half an
inch between the two dishes, the inner dish being supported by
a triangle of platinum wire. Over the inner dish is suspended
a disc of platinum-foil to radiate back the heat into the dish.
The larger platinum dish is heated to bright redness by a triple
gas-burner. An electric mufHe may be used in place of the radi-
ator. This should be run at a temperature of about 500° C.
Heat the dish until the residue is white or nearly so. Note any
blackening or charring of the residue and any peculiar "burnt
odor" which may be given off. After the dish has cooled,
slightly moisten the residue with a few drops of distilled water.
Heat the residue in the oven for an hour; cool in a desiccator
and weigh. This gives the weight of "fixed solids," the differ-
ence being the "loss on ignition." Save the residue for the de-
termination of iron.

Notes. ■ — Before the introduction of modern methods of water-
analysis, the determination of "loss on ignition" was the only
method for the estimation of organic matter in water. In
order, however, that the determination shall possess any real
value, it is necessary to regulate carefully the heat during the
ignition, so as to destroy the organic matter without decompos-
ing calcium carbonate or volatilizing the alkali chlorides.

This is what the use of the radiator or muffle is intended to
accomplish, and in the case of surface-waters with low mineral
content and considerable organic matter, the method gives gen-
erally satisfactory results. But in the case of ground waters
having little or no organic matter and high mineral content,
the loss is often very great on account of the decomposition of
nitrates and chlorides of the alkaline earths and the loss of water
of crystallization. In waters of this class, the determination of
"loss on ignition" is, therefore, generally meaningless, although
an approximation to the amount of organic matter can be ob-

WATER: ANALYTICAL METHODS 89

tained by the addition of sodium carbonate to the water before
evaporating to dryness. By this means, the alkaline earths are
precipitated as carbonates, the chlorine and nitric acid are held
by an alkaHne base, and there is no water of crystallization in
the residue. Even with this modification, the loss is consider-
able when magnesium salts are present, owing to the evolution of
carbonic acid.

It is the practice in some laboratories to ignite over a direct
flame, taking care that the dish does not reach a temperature
above a faint redness.

The behavior on ignition is oftentimes significant. Swampy
or peaty waters give a brownish residue on evaporation to dry-
ness, which blackens or chars, and this black substance burns
off quite slowly. The odor of the charring is like that of char-
ring wood or grain; sometimes sweetish, but not at all offensive.
Waters much polluted by sewage blacken slightly; the black
particles burn off quickly and the odor is disagreeable. Any
observations on this point should be recorded in the report.

Determination of Iron. — This depends on the color produced
by the action of potassium sulphocyanate on ferric chloride.
The color obtained is compared with standards.

Reagents. — The solutions needed are a i-i hydrochloric
acid, a potassium sulphocyanate solution, and a standard iron
solution made from ferrous ammonium sulphate, one c.c. of
this containing o.oooi gram iron (see Appendix B).

Procedure. — Treat the residue from the loss on ignition, or
that obtained by the evaporation of 100 c.c. of the water, with
five c.c. of i-i hydrochloric acid, warming on the steam-bath
or hot plate so as to dissolve as much as possible of the mineral
matter. Wash the solution with distilled water into a loo-c.c.
Nessler tube, filtering if there is any insoluble matter. Make
up to about 50 c.c. with distilled water. Add potassium per-
manganate solution, a few drops at a time, until the solution
remains pink for 10 minutes. This is to oxidize any ferrous
chloride to the ferric condition. Then add 10 c.c. of potassium
sulphocyanate solution and make the volume up to the 100 c.c.

90 AIR, WATER, AND FOOD

mark with distilled water. Iron gives a red color. If iron is
present prepare a blank standard by placing 75 c.c. of distilled
water, five c.c. of hydrochloric acid and 10 c.c. of potassium
sulphocyanate solution in a 100 c.c. Nessler tube. Now add
from a burette, standard iron solution until the color nearly
matches that obtained in the determination. Fill the tube with
distilled water to the 100 c.c. mark and continue adding the iron
solution until the color of the blank exactly matches that of the
determination. From the number of c.c. of standard iron solu-
tion used calculate the amount of iron in the w^ater.

Notes. — In the case of some river-waters, it will be found
necessary to add a few cubic centimeters of hydrochloric acid
to the water while evaporating, in order to facilitate the solution
of the iron. This should be done on a separate portion from that
used for the determination of total solids.

The colors should be matched immediately after adding the
sulphocyanate, since the color fades appreciably on standing.
If the color is greater than that given by 3.5 c.c. of the standard
solution an aliquot part should be used. In this case sufficient
hydrochloric acid and potassium sulphocyanate should be added
so that the same amounts of these are present as given in the
above directions.

Determination of Hardness. — Soap (Clark's) Method.
This method really gives the soap consuming power and not
the true total hardness, but it is in general use for sanitary pur-
poses, and where the water is to be used for household purposes
only, really gives what is most wanted. The determination
depends on the fact that soap forms an insoluble precipitate
with the calcium and magnesium salts in the water. As soon
as the precipitation of the latter is complete a permanent lather
is formed. This serves as the end point. The hardness is
expressed in terms of calcium carbonate per million.

Reagent. — A standard soap solution (see Appendix B).

Procedure. — Measure 50 c.c. of water into a 200-c.c. clear
glass-stoppered bottle and add the soap solution from the burette,
two or three tenths of a cubic centimeter at a time, shaking well

WATER: ANALYTICAL METHODS 9I

after each addition, until a lather is obtained which covers the
entire surface of the liquid with the bottle lying on its side, and
is permanent for five minutes. The number of parts of calcium
carbonate corresponding to the volume of soap solution used is
found in the table in Appendix A.

Notes. — The importance of adding the soap in small quan-
tities cannot be too strongly emphasized, especially in the pres-
ence of magnesium compounds. The presence of magnesium
salts will be recognized by the pecuUar curdy appearance of
the precipitate formed and by the occurrence of a false end point,
the lather lasting about three minutes when the titration is
about half done.

By reference to the table it will be observed that values are not
given for more than 16 c.c. of the soap solution. If in any case
the water under examination requires more than 10 c.c. of the
standard soap solution, a smaller portion of 25 c.c, 10 c.c. or
even two c.c, as the case may require, is measured out and made
up to a volume of 50 c.c. with recently distilled water. If the
volume of soap used is always about seven c.c, this will keep
the results comparable with each other, although the element
of dilution introduces an error. Potable waters, in the eastern
United States, at least, are rarely so high in mineral matter as
to require excessive dilution. In the case of extremely hard
waters, however, the acid method is to be preferred. Distilled
water itself, containing no calcium salt whatever, requires the
use of a considerable quantity of soap to produce a permanent
lather. The cause for this seems to exist in the dissociation
of the greater part of the soap at the extreme dilution to which
it is subjected, and the slow accumulation of a sufficient quantity
of undissociated soap to allow of the increase of surface tension
to a point at which soap-bubbles will persist.

Hehner^s Acid MetJiod* — The temporary hardness of a water
is that part of the total hardness which can be removed by
boiling. It is due to the presence of the bicarbonates of calcium

* Hehner, A)ialyst, 1SS3, 8, p. 77; Draper, Clicm. A^cics, 1885, 51, p. 206; Ellms,
/. Am. Chan. Soc, 1899, 21, p. 239.

92 AIR, WATER, AND FOOD

and magnesium. These give an alkaline reaction to indicators
such as methyl orange and erythrosine, and can be titrated
with standard acid. The results obtained will differ slightly
from the true temporary hardness, on account of the solubility
of calcium and magnesium carbonates which are formed when a
solution of the bicarbonates is boiled, but the results are close
enough for practical purposes.

Permanent hardness is that which is not removed by boiHng,
and is due mainly to the presence of the sulphates and chlorides
of calcium and magnesium. After removing the temporary
hardness by boiling, the permanent hardness, i.e., the calcium
and magnesium remaining in solution, may be determined by
adding standard "soda reagent" (a mixture of equal parts of
sodium hydroxide and sodium carbonate), which precipitates
the magnesium as hydroxide and the calcium as carbonate.
The excess of soda reagent added is then determined by titration
with standard acid, — the amount consumed representing the
calcium and magnesium.

If the original water is neutralized with sulphuric acid all the
temporary hardness will be converted to permanent hardness.
If this latter is then determined, it will represent the total hard-
ness of the sample of water.

Reagents. — The solutions required for the hardness deter-
minations are N/20 and N/50 sulphuric acid, N/io soda reagent,
methyl orange indicator and, for some purposes, erythrosine.

Procedure for Alkalinity. — Measure 200 c.c. of the sample,
filtered if necessary, into a porcelain evaporating dish, add two
drops of methyl orange indicator and titrate to a faint pink with
N/50 sulphuric acid. The end point can best be seen by placing
200 c.c. of distilled water in another dish and adding two drops
of indicator. This gives a standard color and the first change
of the sample being titrated, toward a pink color, can be readily
recognized. The number of c.c. of acid used multiplied by five
gives the alkalinity in parts of calcium carbonate per million.
Save the titrated sample for the determination of total hardness.

If the soap hardness is over 300, a 100 c.c. sample should be

WATER: ANALYTICAL METHODS 93

used. In this case multiply the c.c. of acid by 10 to get the
alkalinity.

Notes. — If the water to be tested has been treated with alum,
erythrosine indicator must be used as methyl orange is not
sufficiently sensitive. For this, measure 100 c.c. of the water
into a clear bottle such as is used for the soap test, and add 2.5
c.c. of the erythrosine indicator (o.i gram of the sodium salt in
one liter of distilled water), and five c.c. of chloroform neutral
to erythrosine. Mix well by shaking and add N/50 sulphuric
acid from a burette in small quantities, shaking thoroughly
after each addition. The pink color in the water gradually
grows lighter until the addition of a drop or two of the acid
causes it to disappear entirely. Make a correction for the indi-
cator by carrying out a blank determination with distilled water.
]Multiply the c.c. of acid used by 10 to get the alkalinity in terms
of calcium carbonate.

Procedure for Permanent Hardness. — Measure 200 c.c. of
water into an Erlenmeyer flask, boil 10 minutes to expel carbon
dioxide, and add 25 c.c. of N/io soda reagent. For waters
with a soap hardness over 300 use a 100 c.c. sample. Boil
down to a volume of about 100 c.c, cool to 20° C, rinse into a
200 c.c. calibrated flask with cooled, boiled distilled water, and
make up to 200 c.c. Mix thoroughly. Filter through a dry
filter paper, receiving the filtrate in a 100 c.c. calibrated flask.
Discard the first 30 or 40 c.c, and then collect 100 c.c. of the
filtrate. Pour into an Erlenmeyer flask, add one drop of methyl
orange indicator and titrate with N/20 sulphuric acid.

Make a blank determination with 200 c.c. of distilled water
in place of the sample.

The difference between the amount of acid required by the
blank and that required in the determination represents the
amount of soda reagent used to precipitate the calcium and mag-
nesium. To get the penuanent hardness multiply this difler-
ence by 25 when a 200 c.c. sample of water is used.

If a water contains sodium or potassium carbonate there wiU
not be any permanent hardness, and hence more acid will be

94 AIR, WATER, AND FOOD

required for the filtrate than corresponds to the amount of
soda reagent added. From this excess the amount of sodium
carbonate in the water may be determined. Any alkah carbon-
ate present would be calculated as temporary hardness by the
direct titration; hence it should be calculated to calcium car-
bonate and subtracted from the results found by the direct
titration.

Procedure for Total Hardness. — Boil down the neutralized
sample obtained at the end of the alkalinity determination to
about loo c.c, add 25 c.c. soda reagent, again boil down to 100
c.c, and proceed as in the determination of permanent hardness.
The calculations are the same as described there.

Free Carbonic Acid. — This determination depends on the
reaction of sodium carbonate with carbon dioxide to form the
bicarbonate,

NasCOs + H2O + COo -> 2 NaHCOa.
As soon as all the free carbonic acid has been used up, the next
drop of sodium carbonate will color phenolphthalein red.

Reagents. — These are an N/22 sodium carbonate solution,
and phenolphthalein indicator.

Procedure. — Measure 100 c.c. of the sample into a tall, narrow
vessel, preferably a 100 c.c. Nessler tube, add a few drops of
phenolphthalein and titrate rapidly with N/22 sodium carbonate
solution, stirring gently until a faint but permanent pink color
is produced.

The number of c.c. of N/22 sodium carbonate solution used
in titrating 100 c.c. of water, multiplied by 10, gives the parts per
million of free carbonic acid as CO2.

Note. — Owing to the ease with which free carbonic acid escapes
from water, particularly when present in considerable quantities,
it is highly desirable that a special sample should be collected for
this determination, which should preferably be made on the
ground. If this cannot be done, approximate results from
water not high in free carbonic acid may be obtained from
samples collected in bottles which are completely filled so as to
leave no air space under the stopper.

WATER: ANALYTICAL METHODS 95

Determination of Sulphates.* — Sulphates can be determined
with an accuracy sufficient for most purposes by means of the
Jackson Candle Turbidimeter.! The results are determined by
the amount of turbidity produced by precipitated barium sul-
phate.

Procedure. — To about 100 c.c. of the water add sufficient
dilute hydrochloric acid (about one c.c.) to acidify and then
one-half a gram of barium chloride. Shake until dissolved.
Pour slowly into the graduated tube of a candle turbidimeter
until the image of the flame beneath just disappears. Read the
height of the liquid in the turbidimeter tube and obtain from
the table in Appendix A the parts per million of sulphates as SO3.

Notes. — Care should be taken to have the solution well
stirred before adding to the turbidimeter tube. The tube must
not be placed over the flame when empty. Waters containing
from 30 to 200 parts per million may be read directly; otherwise
the water should either be concentrated or diluted.

Determination of Alum. — On account of the use of alum or
aluminum sulphate as a coagulant in the filtration of water, a
determination of alumina in the effluent water is often neces-
sary. This may be readily made by the logwood test.|

Procedure. — The logwood solution is made as follows: Take
two grams of logwood chips and boil one minute in a platinum
dish with 50 c.c. of distilled water. Decant the solution and
boil again for one minute with 50 c.c. of water. Decant this
and similarly boil a third time with 50 c.c. of water. Decant
this into a platinum receptacle for use. Take three drops for
each test. Kept in platinum, the solution will last for several
days at least.

Test the water as follows: Boil 50 c.c. of the water in a plat-
inum dish for a short time to expel carbon dioxide. Add three

* "Laboratory Notes on Industrial Water Analysis," Ellen H. Richards. 1910.
J. I. D. Hinds, /. Am. Client. Soc, 18, 661 and 22, 269; D. D. Jackson, J. Am.
Chem. Soc, 1901, p. 799; Muer, /. lud. Eiig. Clieni., 1911, 3, p. 553.

t For a description of this see references.

t E. H. Richards, TecJi. Quart., 1891, 4, p. 194; A. H. Low, Tccli. Quart., 1902,
15. P- 351-

96 AIR, WATER, AND FOOD

drops of the logwood solution and continue boiling for a few
seconds to develop the color. Decant into a glass flask and
cool quickly under the tap (so as not to keep the hot solution
too long in the glass). Transfer to a No. 2 beaker and blow in
carbon dioxide from the breath by means of a glass tube until
there is no further decolorization. Pour the water into a Nessler
tube for comparison with standards similarly prepared from a
standard alum solution. Allow them to stand several hours
before taking the final reading. No wash-water is used at any
of the decantations. The test shows one part of aluminum
sulphate in 8,000,000 parts of water.

Notes. — A blank made with distilled water, if not completely
decolorized by the CO2, will show a tint perceptibly fainter than
that produced by one part in 8,000,000 of aluminum sulphate.

It should be noted that carbon dioxide must be kept absent
until the point prescribed. The solution is, therefore, transferred
to a beaker in order to keep the flask free from carbon dioxide for
the next test.

The main points are:

1. Any kind of logwood appears to answer.

2. The solution is good for several days, at least, if kept in
platinum.

3. The use of platinum instead of glass for boiling the test
solution.

4. The use of carbon dioxide instead of acetic acid.

Aluminum hydrate, as pointed out in 1893 by the late Profes-
sor A. R. Leeds, will produce a tint almost as strong as if it
were in solution, but of a distinctly differing tint.

Low's method of procedure is as follows: First, test the
water as above described. If no tint, or none exceeding that
of the blank, remains after standing several hours or over night,
that is sufficient. If, however, a tint persists, or a colored pre-
cipitate settles out, it is necessary to determine if this is due to
aluminum hydrate. Pour a sample of the water several times
through a double Swedish filter, and finally test the filtrate. If
the tint produced is weaker than that given by the unfiltered

WATER: ANALYTICAL METHODS 97

water, repeat the operation on a fresh portion of the waler,
using the same filter, and continue repeating with new portions
of the water and ahvays using the same filter, until it is apparent
that no further diminution of the tint can be effected.

For a less delicate test in school laboratories where platinum
is not available, the following alternativ'e method may be used:

Dissolve about o.i gram pure ha^matoxylin in 25 c.c. water;
this solution will keep for two weeks and works best after being
made several hours. To 50 c.c. of the water, placed in a four-
inch porcelain dish, add two drops of the ha^matoxylin solution,
allow the solution to stand for one or two minutes, then add a
drop of 20 per cent acetic acid. The standards are prepared at
the same time, using 50 c.c. of distilled water and the required
amount of a standard alum solution. The comparison must be
made immediately, since the color fades on standing. In this
way the presence of one part of aluminum sulphate in five mil-
lion can be detennlned directly in the water and with ease.

Logwood may be used instead of the ha^matoxylin, the solu-
tion being prepared as above.

This test will show the presence of all soluble salts of aluminum
which enter into combination with the coloring matter of the
logwood to form a "lake."

The alkalies and alkaline earths give a purplish color with
logwood extract, hence the test for alum can be made only in
acid solution.

Determination of Lead. — Lead in the minute quantities in
which it ordinarily occurs in water is best estimated by comparing
the color of the sulphide with standards.

Procedure. — If the water is colorless, fill a 100 c.c. Xessler
tube to the mark, acidify with a few drops of acetic acid, and
add from a glass tube one drop of calcium sulphide solution.
A black tint to the precipitated sulphur shows the presence of
lead. A quantitative estimate may be made by comparison
with a series of standards made from a standard lead solution.

If the water is too highly colored to estimate the lead directly,
evaporate three or four liters in a porcelam dish to about 25 c.c,

98 AIR, WATER, AND FOOD

add 10 c.c. of ammonium chloride solution and a considerable
excess of strong ammonia. Then add h}-drogen sulphide water
and allow the dish to stand some hours. Boil the contents of
the dish for a few moments to expel the excess of hydrogen
sulphide, and filter. The precipitate contains all the lead, iron,
and suspended organic matter, also copper and zinc if present,
while the soluble color goes into the filtrate. Wash once with
hot water, transfer the filter to the original dish, and dissolve
the sulphides by boiling with dilute nitric acid (i part acid,
sp. gr. 1.2, to 5 parts water). Filter and wash; evaporate to
10-15 c.c, cool, add 5 c.c. concentrated sulphuric acid and evap-
orate until copious fumes are given off. Then, if the original
water contained less than 0.25 part iron per million, add acetic
acid and ammonia, boil, filter and read the amount of lead in
the alkaline filtrate, making the standards also alkaline with
ammonia.

If the water contained over 0.25 part iron, wash the lead
sulphate into a beaker with alcohol and water, and let it settle
overnight. Filter, wash free from iron with 50 per cent alcohol,
dissolve the precipitate by boiling with ammonium acetate,
filter, and determine the lead as above.

Note. — If more than 0.25 part of iron is present, some of
the lead will be held by the precipitated ferric hydroxide; and
if 25 parts are present, all of the lead may be lost in this way;
hence the modification of the method in the presence of consider-
able quantities of iron.*

When copper is also present it is detected by the blue color
given to the ammoniacal filtrate from the iron precipitation.

Determination of Phosphates, f — Procedure. — Evaporate 50
c.c. of the water and three c.c. of nitric acid (sp. gr. 1.07) to
dryness in a three-inch porcelain dish on the water-bath. Heat
the residue in an oven for two hours at the temperature of boiling
water. Treat the dry residue with 50 c.c. of cold distilled water,

* EUms, J. Am. Chem. Soc, 1899, 21, p. 359.

t Lepierre, Bull. Soc. Chim., 1896, 15, p. 1213; Woodman and Cayvan, /. Am.
Chem. Soc, 1901, 23, p. 96; Woodman, ibid., 1902, 24, p. 735.

WATER: ANALYTICAL METHODS 99

added in several portions and poured into the comparison-tube.
It is not necessary to filter the solution. Add four c.c. of ammo-
nium molybdate (50 grams per liter) and two c.c. of nitric acid,
mLx the contents of the tube and compare the color, after three
minutes, with standards made by diluting varying quantities
of the standard phosphate solution (i c.c. = o.oooi gram P2O5)
to 50 c.c. with distilled water and adding the reagents as above.
Carry out a blank determination on the distilled water used for
dilution, especially if it has stood for any length of time in glass
vessels.

Notes. — The method as described will be sufficient for ordi-
nary work. If a more exact determination of the phosphate is
required, a slight correction should be made in each case. For
a table showing these corrections reference may be made to the
paper by Woodman and Ca}"\^an previously cited.

The evaporation and heating with nitric acid is for the purpose
of removing silica, which gives with ammonium molybdate a
yellow color similar to that given by phosphates.

The determination of phosphates in a drinking-water is a
matter which has not received the attention from water analysts
that has been given to the estimation of various other con-
stituents. Any one who looks through the literature cannot
help noticing how few are the published results of quantitative
estimations of the phosphate content of natural waters, apart
from mineral waters. Yet this determination, by reason of the
conversion of organic phosphorus compounds into phosphates
through the process of decay, is one which might reasonably
be expected to throw considerable light on the question of the
pollution of natural waters by objectionable material.

The reasons for this dearth of published data are not far to
seek. To be of value the amount of phosphate must be known
within rather narrow limits. Qualitative tests are not sufficient.
The mere presence of phosphates is by no means definite or
even confirmatory evidence of organic pollution. Rocks and
minerals containing phosphates are found nearly ever>"svhere,
and traces, at times even considerable quantities, may be dis-

lOO AIR, WATER, AND FOOD

solved, especially by waters rich in carbonic acid. This, how-
ever, does not constitute a serious objection to the utility of the
determination. The same is true of many, if not most, of
the constituents upon which reliance is placed in judging of the
quahty of a water. Unpolluted waters often contain notable
amounts of nitrates and chlorides, and a true judgment can be
rendered only after comparison with samples from adjacent
but unpolluted sources.

The chief reason, however, has been the lack of an accurate
and simple method, sufficiently delicate, and of enough data
to work out a standard for comparison.

This reason can hardly hold true now, for enough work has been
done on the colorimetric method to indicate its value as another
link (of which we have none too many, anyway) in the chain of
circumstantial evidence by which we are often compelled to
judge the purity of a water.

The amount of phosphate and its variation seem to follow
the same general line as the other mineral constituents which
either accompany the polluting material or are produced by its
decay, especially the nitrates and chlorides. It is not, however,
so delicate an indicator as these. In general, it may be said
that the amount (expressed as P2O5) in an unpolluted water will
seldom be over i.o part per million.

Determination of Dissolved Oxygen. — Winkler Method* — -
The method depends on the absorption of oxygen by man-
ganous hydroxide with the formation of manganese dioxide;
the liberation of iodine by this last in an acid solution contain-
ing potassium iodide; and the titration of the iodine with sodium
thiosulphate. The reactions involved can be expressed as
follows :

MnS04 + 2 NaOH -^ Mn (0H)2 + Na2S04.

2 Mn(0H)2 + O2 -^ 2 Mn02 + 2 H2O.

Mn02 + 2 H2SO4 + 2 KI -^ MnS04 + I2 + K2SO4 + 2 H2O.

2 NaoSaOs + lo -^ 2 Nal + Na2S406.

* Berichte, 1888, 21, p. 2843; also see "Standard Methods of Water Analysis."

WATER: ANALYTICAL METHODS

lOI

The method has recently been modified by Hale and Melia*
by titrating the iodine in an acetic acid solution in order to
avoid difficulties due to the presence of nitrites and nitrates,
and this should be followed in testing for putrescibility.

Collection of Samples. — The samples are collected in glass-
stoppered bottles of known capacity, holding about 300 cubic
centimeters. When water is taken from a faucet, the bottle
is filled by means of a tube which passes to the bottom of the
bottle. A considerable amount of water is allowed to pass
through the bottle and overflow at the top. It will be almost
impossible to obtain duplicate samples unless the bottles are
filled at the same time by means of a T tube, owing to varia-
tions in pressure in the pipes.

In taking samples from a stream or pond, a stopper with two
holes is used. A tube passing through one of these holes is
sunk in the water to the desired depth,
and the other is connected with a larger
bottle of at least four times the capacity
of the smaller one, and fitted in the same
way. From the larger bottle the air is
exhausted by the lungs or by an air-pump
until it is nearly filled with water. Unless
the determination is to be made at once,
the rubber stopper of the smaller bottle is
quickly replaced by the glass stopper so
that no air is left in the bottle. The tem-
perature of the water at the time of sam-
pling should be noted.

The apparatus which has been used in
connection with work in this laboratory
for collecting samples at various depths
down to 75 feet is shown in outline in
Fig. 10. A galvanized-iron can of such
size as to hold one of the gallon bottles is weighted with
lead and provided with ears at the top for suspending. The
* /. Ind. Eng. Cliem., 1913, 5, p. 976.

Fig. 10.

I02 AIR, WATER, AND FOOD

bottle, which is securely wired in, is provided with a rubber
stopper carrying two brass tubes, one ending just below the
stopper and projecting for about 8 or 9 inches above it, the
other extending to the bottom of the bottle and connected by
heavy rubber tubing with the sample bottle. This is held by
brass brackets, which are fastened by means of a wooden cleat
to the side of the can. The neck of the bottle is put into the
slot in the upper bracket and then it is firmly clamped by the
thumb-screw of the lower one. The arrangement of tubes in
the sample bottle is obvious. In using the apparatus it is
quickly lowered to the desired depth by means of a rope marked
off in feet. The water enters the sample bottle and flows through
it into the other. When the bubbles cease to rise, indicating
that the larger bottle is full, thus replacing the water in the sam-
ple bottle a number of times, the apparatus is drawn to the
surface. The temperature is read from a thermometer fastened
to the tube inside the gallon bottle.

Reagents. — The reagents needed are solutions of man-
ganous sulphate, potassium iodide in sodium hydroxide, potas-
sium acetate, N/ioo sodium thiosulphate, and starch indicator
(see Appendix B).

Procedure. — Remove the stopper from the 300-c.c. cali-
brated bottle, and add two c.c. of manganous sulphate solution
with a pipette having a long capillary point reaching to the
bottom of the bottle, and in the same way add two c.c. of the
solution of sodium hydroxide and potassium iodide. Insert
the glass stopper, leaving no bubbles of air, and mix the contents
of the bottle. Allow the precipitate to settle, remove the stopper
and add two c.c. of concentrated hydrochloric acid from a
pipette in the same manner as before. Replace the stopper,
driving out some of the liquid, and shake until the precipitate
is dissolved, and the Hquid homogeneous. Remove 100 c.c.
with a pipette or graduated flask, and titrate with N/ioo sodium
thiosulphate, using starch as an indicator. Add the starch
solution, about two c.c, only after the iodine solution has be-
come a light straw color.

WATER: ANALYTICAL METHODS

103

To calculate the results proceed as follows: Let V equal the
volume of the bottle with the stopper inserted and N the number
of c.c. of thiosulphate used. One c.c. of N/ioo sodium thio-
sulphate is equivalent to 0.00008 gram of oxygen. The actual
volume of water from which the oxygen was removed is equal
to the volume of the bottle minus the four c.c. displaced by the
first two reagents added. The liquid displaced by the acid does
not need to be allowed for, as it did not contain any oxygen or
iodine. The oxygen equivalent to the iodine titrated in the
100 c.c. of the solution removed is equal to N X 0.00008.

The oxygen equivalent to the total iodine liberated is equal to

N X 0.00008 X V
100

This is the oxygen present in the original water, which has a
volume of (F — 4), the four c.c. being the part displaced by the
solutions added. The oxygen in parts per million is, therefore,
equal to

N X 0.00008 X F X 1,000,000 ^ 0.8 iVF
100 X (F - 4) ~ F - 4 '

If the sodium thiosulphate solution is not exactly N/ioo, the
correct oxygen equivalent should be substituted in place of the
value 0.00008.

QUANTITIES OF DISSOLVED OXYGEN IN PARTS PER MILLION

BY WEIGHT IN WATER SATURATED WITH AIR AT THE

TEMPERATURE GIVEN

Temp.
C.

Oxygen.

Temp.
C.

Oxygen.

Temp.
C.

O.xygen.

Temp.

Oxygen.

14.70

11.86

9-94

8.51

14.28

11.58

9-75

8.35

13-88

II. 31

9 56

8.19

13 SO

11.05

9-37

8.03

13 14

10.80

9.19

7.88

12.80

10.57

9.01

7-74

12.47

10.35

8.84

7.60

12.16

10.14

8.67

104 AIR, WATER, AND FOOD

The results of this determination are frequently expressed in
per cent of saturation, which is given by the ratio of the oxygen
found to that present if the water were completely saturated
at the same temperature. The latter figure is given by the
preceding table.

Procedure to he Followed in Putrescihility Tests or with Polluted
Waters f^ — ■ Follow the directions as given above until after the
addition of the concentrated hydrochloric acid. Then replace
the stopper and shake until all the precipitate is dissolved.
Remove the stopper and add from a pipette two c.c. of potassium
acetate solution. Mix by pouring into a flask or beaker and
back into the bottle. Remove loo c.c. as before and titrate
with N/ioo sodium thiosulphate.

The addition of the acetate increases the volume of the iodine
solution from V (the volume of the bottle) to (F + 2), and this
should be substituted in the formula given on p. 103. The oxygen
in parts per million will, therefore, be equal to

0.8 N {V + 2)
F-4

Notes. — If water is collected in the ordinary way and trans-
ferred to the apparatus by pouring, there will inevitably be
an absorption of oxygen unless the water is already saturated.
Thus a process which gives excellent results when the water is
nearly or quite saturated may fail entirely to give accurate
results when the dissolved oxygen is low or absent. The water
may be supersaturated with oxygen in which case the per cent
of saturation may be more than 100. f

Determinations of dissolved oxygen in ponds and streams are
best made on the spot, or, at least, the reagents should be added
until after the addition of the hydrochloric acid. The very
simple apparatus required for the Winkler process can be packed
in a small space, and the entire determination requires only a
few minutes. The absorption of the oxygen by the manganous

* See article by Hale and Melia, loc. cit.
t Gill, Tech. Quart., 1892, 5, p. 250.

WATER: ANALYTICAL METHODS 105

hydroxide is complete almost at once, and it is unnecessary to
allow it to settle for a long time before adding the acid. The
titration can be made with a small burette or pipette with
accurate results.

Putrescibility Test.* — There is at the present time no really
satisfactory standard putrescibility test. One which seems to
have been worked out on logical principles and which has given
satisfaction in this laboratory is that proposed by the Royal
Sewage Commission. The putrescibility is measured by the
absorption of dissolved oxygen under given conditions. A
stream water or diluted sew^age or effluent, — the water used
for dilution furnishing the necessary oxygen, — is tested for
dissolved oxygen. A sample is then incubated in a closed bottle
for five days at 20° C. and the dissolved oxygen again deter-
mined. The difference represents the oxygen absorbed, and
should not be greater than 20 parts per million.

Procedure. — If the water is from a stream or lake, fill com-
pletely two 300-c.c. calibrated glass-stoppered bottles. Insert
the stoppers, taking care that no air bubbles are enclosed. If a
sewage or effluent is being tested, make dilutions with tap water
as follows:

Raw sewage. Dilute 6 c.c. to 600 c.c.
Settling tank effluents. Dilute 12 c.c. to 600 c.c.
Filter effluents. Dilute 120 c.c. to 600 c.c.
Fill two calibrated bottles as just described.

Make a dissolved oxygen test on one bottle, following the
directions as given for putrescibility tests. Set the other bottle
in a 20° incubator and let stand for five days. Then determine
the dissolved oxygen agam. Calculate the results in terms of
oxygen absorbed by the original sample of water, sewage or
effluent.

Determination of the Color. — The amount of color is gen-
erally determined by direct comparison of the water with some
definite standard of color. Various standards have been pro-

* Eng. Rcc, 1913, 68, pp. 315 and 453; Am. J. Pub. Health, 1914. 4, p. 2.^1.

Io6 AIR, WATER, AND FOOD

posed, the objection to most of them being that they are not
sufficiently general in their application, being adapted only for
the color of some particular class of waters.

The standard in most general use is the platinum standard.
The comparisons of the water with the color standards are most
readily made in 50-c.c. Nessler tubes. According to this scale,
the color of a water is the amount of platinum in parts per
million, which, together with enough cobalt to match the tint,
must be dissolved in distilled water to produce an equal color.
In practice, a standard having a color of 500 is prepared by dis-
solving 1.246 grams of potassium platinic chloride (equivalent
to 0.5 gram platinum), i.o gram of cobalt chloride (equivalent
to 0.25 gram cobalt), and 100 c.c. of strong hydrochloric acid in
distilled water and diluting to one liter.

Dilute standards for use are made by diluting varying amounts
of this standard to 50 c.c. with distilled water. Thus, by dilut-
ing one c.c, two c.c, and three c.c. each to 50 c.c, colors of 10,
20, and 30 are obtained. It is claimed that the platinum
standards are permanent if protected from the dust, but in this
laboratory it has been found necessary to replace them about
once a month.

Determination of the Odor. — Cold. — Shake violently the
sample in one of the large collecting-bottles when it is about
half or two-thirds full, then remove the stopper and quickly
put the nose to the mouth of the bottle. Note the character
and degree of intensity of the odor, if any. An odor can be often
detected in this way which would be entirely inappreciable if
the water were poured into a tumbler.

Hot. — Pour into a plain beaker about five inches high enough
water to one-third fill it. Cover the beaker with a well-fitting
watch-glass and place it on an iron plate which has been pre-
viously heated, so that the water shall quickly come to a boil.
When the air bubbles have all been driven off and the water is
about to boil, take the beaker from the plate and allow it to cool
for about five minutes. Then shake it with a rotary movement,
slip the watch-glass to one side and put the nose into the beaker.

WATER: ANALYTICAL METHODS 107

Note the odor as before. The odor may or may not be the same
as that of the water when cold; it can be perceived, as a rule,
for only an instant.

Notes. — It is inevitable that a certain personal equation
should influence this test. Each laboratory will have its own
standards for routine work, but a certain familiarity with the
more common odors will tend to allay public anxiety and to aid
in a more watchful habit on the part of consumers. Good
ground waters do not give distinct odors unless they are derived
from clayey soil, but the odor often betrays a contaminated
well. Surface-waters will nearly always yield a characteristic
odor. This odor may be due to the organic matter contained
in the water, or to the presence of minute plants or animal
organisms.

Among the odors which are frequently met are "earthy,"
"vegetable," "musty," "mouldy," "disagreeable," and "offen-
sive." The "earthy" odor is that of freshly turned clayey soil.
"Vegetable" is the odor of many normal colored surface-waters;
it may be described as swampy or marshy, pond-like, and is
often strengthened by heating. "Musty" can be likened to
the odor of damp straw from stables; it is fairly characteristic
of sewage contamination, and by the trained observer is dis-
tinctly distinguishable from the mouldy odor. "Mouldy" is
the odor of upturned garden or forest mould, or of a moist hot-
house; it is somewhat alHed to the earthy odor. "Disagree-
able" is a term which is capable of wide variation among different
observers. It may include certain characteristic odors which
are peculiar to the growth or decay of certain organisms, as the
"pigpen" odor of AnahcBna, the "fishy" or "cucumber" odor
of Synura, etc. The term "offensive" is generally reserved for
the sewages. These terms can be taken only as broad illustra-
tions of the character of the particular odor, since the odor will
very likely be described by different persons in different ways,
and each laboratory will have its own characterization. The
odor which often accompanies an abundant development of
diatoms is a good illustration of this. It will be called bv various

Io8 AIR, WATER, AND FOOD

inexperienced observers offensive, rotten, fishy, geranium-like,
aromatic, in one and the same sample of water.

The terms generally used to signify the degree of intensity
of the odor are "very faint," "faint," "distinct," and "decided."
The exact value to be placed upon each of these terms will, as a
matter of course, vary with the individual analyst, but in a
general way, it may be said that the "very faint" odor is one
that would not be detected except by the trained observer; the
"faint" odor would be recognized by the ordinary consumer if
his attention were called to it; the "distinct" odor is one that
would be readily noticed by the average consumer, but would
not interfere with the use of the water; while the "decided"
odor ^ is one which would, in all probability, render the use of
the water unpleasant.

Determination of the Turbidity and Sediment. — The sus-
pended matter remaining in the water after it has rested quietly
in the collecting-bottle for twelve hours, or more, is called its
turbidity, and that which has settled to the bottom of the bottle,
its sediment.

Good ground waters are often entirely free from turbidity
and sediment, the suspended matters having been filtered out
during the subterranean passage of the water, but this is rarely
true of surface-waters. The turbidity is various in character
and amount, sometimes milky from clay or ferrous iron in solu-
tion ; usually it consists of fine particles, generally living algae or
infusoria. These often collect on the side toward or from the
light, and a practiced eye can, not infrequently, recognize their
forms. Some of the lower animal forms can also be seen by the
naked eye, and the larger Entomostraca are quite noticeable
in many waters.

The sediment may be earthy or flocculent; in the latter case
it is generally debris of organic matter of various kinds. The
degree of turbidity is expressed by the terms "very sHght,"
"slight," "distinct," and "decided," and the degree of sedi-
ment by "very slight," "slight," "considerable," and "heavy."
These determinations, again, are of value only to the routine

WATER: ANALYTICAL METHODS

109

worker, and for him there are various methods in use. The
papers of Pannclce and Ellms * and of WTiipple and Jackson t
should be consulted for a description of these.

Sewage Analysis.^ — The methods for the analysis of sew-
ages and sewage effluents are the same as those described for
water. The main difference is in the quantities used for the
various determinations. In most cases, this has been noted in
connection with the analysis. Great care should also be exer-
cised in taking samples from a bottle as the large amount of
suspended matter makes it more difficult to obtain a represent-
ative portion. Special attention is called to the putrescibility
test (p. 105) for effluents, as stability is the main desire in treat-
ing a large proportion of sewages.

Biological Examination. — Since a large number of, if not all,
diseases are caused by living organisms, it would seem most
desirable in examining a water supply if the specific organisms
causing water-borne diseases could be looked for, and, if present,
isolated. However, it is quite impossible to do this in the great
majority of cases, and so in bacteriological work, just as in
chemical analysis, certain indications of the presence of sewage
are sought for, and if these indications are positive, the water
is condemned. In a bacteriological examination, the most
important index of the presence of sewage is finding B. coU in
quantities as great as one in each cubic centimeter. This
organism is a normal inhabitant of the intestines of man and
the higher animals and is present in large numbers in human
and animal excreta. Its presence, therefore, in water shows
the presence also of sewage. For a discussion of water bacteri-
ology and methods of analysis the reader is referred to another
book.§

The close relation of the odor to the living flora and fauna of

* Tech. Quart., 12, 1899, p. 145.
t Ihid., p. 283.

X See Fowler "Sewage Works .Analyses," John \\ilcy & Sons, 1902.
§ Prescott and Winslow, "Elements of Water Bacteriology," 3rd edition.
John Wiley & Sons, 19 13.

no AIR, WATER, AND FOOD

the water makes it desirable that the chemist shall be able to
recognize the more common forms of water plants and animals,
even if he make no pretensions to a knowledge of cryptogamic
botany or of zoology. Therefore, a microscope and a concen-
tration apparatus should be in every water-laboratory. A full
description will be found elsewhere.*

* Whipple, "The Microscopy of Drinking Water," 3rd edition, John Wiley
& Sons, IQ14.

CHAPTER VII

FOOD IN RELATION TO HUMAN LIFE: COMPOSITION,
SOURCES, DIETARIES

Life itself is conditioned on the food-supply. WTiolesome
food is a necessity for productive life. IMan can and does exist
on very unsuitable, even more or less poisonous, food, but it is
merely existence and not effective life. This is true not onl}- of
the wage-earner, but of the business-man, the professional man,
the scholar. To be well, to be able to do a day's work, is man's
birthright. Nevertheless, a too large proportion of the American
people sells this most valuable possession for a mess of pottage
which pleases the palate for three minutes and weights the diges-
tive organs for three hours. With the products of the world ex-
posed in our markets, the restraints of a restricted choice, as well
as inherited instincts or traditions, lose their force. The buyer,
unless he has actual knowledge to guide him, is swayed b\- the
caprices of the moment or the condition of his purse, and often
fails to secure adequate return in nutritive value for the money
paid. The fact that so much manipulated material is put upon
the market renders this choice of food doubly difficult, since the
appearance of the original article is often entirely lost, and to
city-bred buyers even the natural product conveys little idea of
its money value. It is now even more necessary that an elemen-
tary knowledge of the proximate composition and food value of
the more common edible substances should be recognized as an
essential part of education.

Food: Definition and Uses. — Food is that which builds up the
body and furnishes energy for its activities: that which brings
within reach of the living cells which fonn the tissues the elements
which they need for life and growth. Only such available sub-
stances can be called food, no matter what their chemical compo-

112 AIR, WATER, AND FOOD

sition may be. Soft coal contains carbon and hydrogen and is
food for the furnace, but is not available for the animal body.

This food which is taken into the body is used in various ways.
It forms and builds up new tissues, besides repairing and making
good the waste of tissues due to bodily activity ; it is stored up in
the body to meet a future demand; it supplies the needed heat
by the transformation of its stored up or potential energy into
the muscular energy required by the body; it may be used to
protect the tissues of the body from being themselves consumed
as food.

Composition of Food. — We determine what chemical elements
enter into the composition of the body by an analysis of the vari-
ous organs and tissues. We learn what combinations of these ele-
ments serve as food by determining those present in mother's milk
and in foodstuffs which experience has proved to furnish perfect
nutrition. From these studies it is apparent that about fifteen
chemical elements are constant constituents of the human body;
that about a thousand natural products are known to have food
value; that of these, one hundred are of world-wide importance
(see table, page ii8), and that ten of them form nine-tenths of
the food of the world.

The composition of food, as shown by chemical analysis, is
not, however, the only factor that must be known to determine its
value. The digestibility of the material must be taken into ac-
count as well. "We live not upon what we eat, but upon what
we digest." It is more important to know the amount of availa-
ble nutrients than the amount of total nutrients.

Food Principles. — While the foodstuffs present great variety,
the food principles may be grouped under four headings; viz.,
nitrogenous substances or proteids, fats, carbohydrates, and
mineral salts. Each group contains many members with minor
but often essential differences. To make these substances
available, there is needed an ample supply of air and of water,
— of water for solution and circulation, of air for the oxygen
needed to liberate the stored energy of the food in the place
where it will accomplish its purpose.

FOOD IN RELATION TO HUMAN LIFE 113

Nitrogenous Substances. — Since, in some way as yet un-
known to us, nitrogen is essential to living matter, such sub-
stances as contain this element in an available form arc of the
first importance. Some, as albumen, are so closely allied to
human protoplasm that probably they need only to be dissolved
to be at once assimilated. Others, as gluten and similar vege-
table products, undergo a greater change; while still others,
as gelatine, have a less profound but marked effect in protecting
the tissues from waste.

The" enzymes, "ferments," in part, of the older nomencla-
ture, are also highly nitrogenous substances present in some
form in nearly all foodstuffs of natural origin. The nearer the
composition of the food approaches that of the protoplasmic
proteid, presumably the greater its food value, since each cleav-
age, each hydrolysis, each step in the breaking down of the
highly complex molecule, consisting of hundreds of atoms, is
supposed to liberate the stored energy. Therefore, it is not a
matter of indifference in what form this essential is taken. So
little is known, however, with scientific accuracy that students
will find a fruitful field of research along these lines of inves-
tigation. Also together with this element, nitrogen, go others,
in small quantity to be sure, but evidently of great value. Such
are sulphur, iron, phosphorus. One difference between the
several groups of proteids is seen in this combination with the
metallic elements which seems to carry with it certain effects.
Until greater progress has been made in determining the
availability in the organism of the various known substances,
we must be content with a wide margin in the calculated quan-
tities necessary for the daily efficiency, except in the very few
instances of nearly pure substances, as white of egg. It is
evident, also, that the manner of preparation and the kind of
mixtures used in food will affect most profoundly so unstable
and complex a class of substances. One thing is certain, that
the body cannot take nitrogen from that which does not contain
it. Therefore, a certain quantity of highly nitrogenous food
should form a portion of the daily supply. It is usually held

114 AIR, WATER, AND FOOD

that the body seems to be sufficiently nourished when the food
contains an amount of digestible proteid equivalent to about loo
grams of dry albumen per day for the average adult, although
recent work has shown that this figure is probably too high.
An excess appears to have a stimulating effect and overloads
the system with the waste, since the end-products are not purely
mineralized substances, as are carbon dioxide and water from
the carbohydrates, but are compounds of an organic nature,
as creatin, urea, and uric acid, which have deleterious effects
when accumulated in the system. A deficiency of nitrogen is
made good, to a limited extent, by the protective agency of the
other foodstuffs which offer themselves for all the offices except
the final one of tissue-building.

Fats. — For this protective action, as well as for many other
purposes, the fats are most valuable, and if they occur in about
the same proportion as do the nitrogenous elements, the needs
of the organism seem to be well met. Thus, in mother's milk,
in eggs, and in meat from active animals these two are in nearly
equal proportions, while in the cereals the fat is less; in nuts
and in meat from fattened animals, as a rule, it is higher than
the nitrogen. Little is known as to the varying food value of
these fats from different sources. Certain physical conditions
of solidity, melting-point, etc., seem to have more influence
than mere chemical composition. Whatever the source, it is
certain that the stored-up energy which is to serve the organism
in cases of loss of income from any cause is in the form of fat,
a form which is not subject to the action of agents which so
readily decompose proteids and carbohydrates and yet is readily
converted into available food whenever called for. That it is
not absolutely necessary that the food should contain fat as
such seems to be proved by experiment, but from the fact that
nearly all natural food-substances do contain it, and that it
appears to be more economical of human energy to take it from
these foods than to manufacture it from the proteids and carbo-
hydrates, we may safely assume fat to be an essential of the
human dietary.

FOOD IX RELATION TO HUMAN LIFE 115

That the equality in amount of fat with nitrogenous com-
pounds is not essential is proved by the fact that the strong
draft animals, as horses and oxen, take food in which the per
cent of fat is not more than half as much as of proteid; never-
theless, it is present in the food of all animals and doubtless,
in its turn, is protected by an excess of the third class of food-
stuffs, the carbohydrates, characteristic of the vegetable king-
dom — a class which in the final decomposition, yields clean
volatile products, water and carbon dioxide, and which, there-
fore, do not clog the system so readily as do urea and other
wastes.

Carbohydrates. — The number of more or less well-defined
substances under this head is legion: starches from scores of
plants, sugars from as many more, gums, pectins, and dextrins,
all with a certain food value, dependent probably upon the
utilization of the various mixtures with which they are taken
into the alimentary canal. These foodstuffs are very liable to
*' fermentation," that is, to an acid decomposition which pre-
vents their absorption by the delicate lining of the walls of the
intestines and which causes digestive disturbance. The sugars,
which are very soluble, and, therefore, liable to be present in
excess, are especially subject to this change. This class of
food-substances is found in the diet of civilized man, free to
choose, in an amount about equal to the sum of the other two
classes, with a tendency to less rather than more. It may be
said that sugar and fat increase over starch in the diet of a people
of unrestricted choice, but it is not certain that the qualities of
body which make for hardihood and resistance to disease are
correspondingly increased. There is, indeed, much evidence
to show that power of digesting vegetable foods indicates a
general well-being of body conducive to long life. A ready
adaptation renders possible the changes of habitat required by
civilization. Unless one is to be confined to a narrow range, it
is wise to cultivate a strength of digestion as well as a strength of
muscle, and for the best brain power we believe it to be more
essential.

Il6 AIR, WATER, AND FOOD

Mineral Salts. — The fourth class, mmeral salts, comes into
the food largely from the vegetable substances eaten, for in
these the union is an organic one readily assimilated. As we
have seen, certain elements go with the nitrogenous portion,
as, for example, in gluten and its congeners are found sulphur
and phosphorus. Potassium, found in barley, is a constant
constituent of protoplasm, while sodium is found in blood-
serum. A lack of vegetable foods seems to impoverish the
blood-corpuscles. For children, a deficiency in lime causes
serious disease. Sugar, olive-oil, corn-starch and other prepared
food-substances cannot take the place of asparagus, cabbage,
carrots, etc.

To sum up briefly, then, we may say that the protein or nitrog-
enous portion of the food forms tissue, such as muscle, sinew and
fat, and furnishes energy in the form of heat and muscular
strength; the fats build up fatty tissue, but not muscle, and
supply heat; the carbohydrates are changed into fat and supply
heat. Another important use of the nutrients is to protect
each other from being used in the body. The carbohydrates,
especially, in this way protect the protein, including muscle,
etc., from consumption.

Change in Composition Due to Cooking. — The composition of
cooked foods is in general not the same as the raw material on ac-
count principally of chemical and physical changes brought about
by the heat employed in the cooking process. The total nutri-
ents, calculated on a water-free basis, may be practically the
same, but the structure is often quite different.

Starch is hydrolyzed and rendered soluble by heating in the
presence of moisture, and at higher temperatures it may be
converted into the brown, soluble dextrin. The sugars are
changed, being, in the case of sucrose, partly converted into
other forms, such as invert sugar, by the heating, with the help
of the organic acids present in many foods. Some of the proteids
tend to become less soluble through heating and at higher tem-
peratures may be even partly decomposed with possible loss of
food value.

FOOD IN RELATION TO HUMAN LIFE 117

Eeai of Combustion. — Until a more definite knowledge of the
processes of metabolism (the transformations of matter and
energy in the animal organism) is obtained the potential energy
of food is calculated in terms of mechanical work — expressed
in heat-units or calories.

One calorie is the amount of heat rcc^uired to raise the tempera-
ture of one gram of water one degree centigrade. A gram of fat,
as actually digested and oxidized in the body, affords enough
heat to raise the temperature of about 9000 grams of water one
degree. In like manner a gram of protein has an energ>'-pro-
ducing power expressed in calories of about 4000, and for carbo-
hydrates the average value is also 4000.

Allowance is made in these figures for the fact that to digest
completely any part of our food results in a decrease of the
amount of energy to be derived from it, and this affects the
protein more than it does the other two. It is probably true
that under favorable conditions the fat and carbohydrates
can be completely utilized in the body and consequently their
energy-producing power can be correctly estimated from their
heat-producing power outside the body. In the case of pro-
tein, however, the digestion within the body is never so com-
plete as to furnish all the energy that would be obtained by a
complete combustion of these nitrogenous materials outside of
the body.

The fact remains, however, that all experiments yet made go
to show that within practical limits we are safe in using the heat
of combustion (expressed in calories) of any food-substance as a
controlling measure of food values.

Nutritive Ratio. — The requisite number of calories must, how-
ever, be obtained by the utilization of such substances as contain
all the elements needed by the body, and in such ratio as has been
found available for the balance of nutrition. In carrying on its
multifarious activities the body loses about 20 grams of nitrogen
per day, which must be replaced by the same element in the food
taken. Thus while the requisite number of calories may be fur-
nished by fat or starch, these substances alone will not suffice for

ii8

AIR, WATER, AND FOOD

COMPOSITION OF SOME COMMON FOOD-MATERIALS AS PURCHASED

I. Fuel Value 3000-4000 Calories * per Pound

Food-material.

Butter

Lard (refined). . . .
Oleomargarine. . .

Salt fat pork

Suet

Walnuts (shelled).

Refuse.

Per cent.

Water.

Per cent.

II. o

9 5
0.3 to 12.2
4.3 to 21.9

2.5

Nitroge-
nous
Substances

Per cent.

0.2 to 5.0

I.I to7S

16 6

Fat.

Per cent.
85.0
100.00
83.0
80 . 3 to 94 . 1
70.7 to 94. S
63 4

II. Fuel Value 2000-3000 Calories per Pound

Bacon

Cheese (American pale).

Chocolate

Doughnuts

Mutton flank (fat)

Peanut butter

Sausage (farmer)

8.7

3.9

18.4

31.6

5 to 10

Ot0 25

28.9
2.1
22.2

9 5
28.8
12.5 to 13.4
S.I to 76
10.7
29 3
27.9

59.4

35 9
47.1 to 50.2
16.4 to 25.7

59.8

46. S

40.4

Carbo-
hydrates.

Per cent.

0.3
26.8 to 33-8
45-8 1063.2

III. Fuel Value 11:00-2000 Calories per Pound

Barley (pearled )

Beans (dried)

Cake average (except fruit) . . .

Candy

Cheese (.NIeuchatel)

Corn meal

Corn -starch

Crackers (average)

Fat meats

Gelatin

Ham (smoked, medium fat).
Infants' and invalids' foods..

Macaroni

Oats

Peanuts

Peas (dried)

Pop-corn

Rice

Rye flour

Sugar (granulated)

Wheat (entire) flour

Wheat flour (white bakers').

Wheat (shredded)

Zwieback

11. 7

4.5 to 28.4

9.8 to 12.9

9.6 to 15 5

19.9

4.0

42.7 to 57-2

8.8 to 17.9
10. o

6.8

38.3

13.6

27.3 to 42.5

2.4 to 12.3

7.0 to 12.3

7.8
6.9

6.9 to 15.0
4 3

9.1 to 14.0
II. 9 to 13.6

6.4 to 13. 1
10. I to 13.3
7.2 to 10 7
5.0 to 7-7
* Including fibre

7.0 to 10. 1

19.9 to 26.6

6.3

15. 1 to 22.3
6.7 to II. 6

10.7
13 0
84.2

10.2 to 21.9
2.0 to 22.5
7.9 to 16.6

16. S

19.5
20.4 to 28.0

10.7
59 to II. 3
4.9 to 8.8

12.2 to 14.6

10.3 to 14.9
9.6 to II. 4
8.6 to II. 7

o.7to i.s

1.4 to3.l

9.0

22.3 to 32. 5

l.otos.3

8.8

36.8

24.S to39.9

0.3 to 10.9

0.0 to 4.9

7 3

29.1

0.8 to 1.3

o.i to 0.7

0.2 to 1.3

I.S to 2.1

1.9 to 2.0

1.3 to 1.6

8.1 to II. 3

77-3 to 78.1*
57-2 to 63.5*

63.3

96.0
0.2 to 2.9
68.4 to 80.6*

90.0*

71 9*

66 . 9 to 89 . 4

67.2 to 78.4*
66. s*
18. S

58.0 to 67.4*
78.7

75. 4 to 81.9*
77.6 to 80.2*

100

69.5 to 770*

70.3 to 75 S

75.0 to 79-7*

72.1 to 74.2

IV. Fuel Value 1000-15000 Calories per Pound

Apples (dried)

Bread (white)

Corn-bread

Dates

Figs

Fresh pork (ribs and shoulder).
Medium fat mutton and beef. .

Mince-meat (commercial)

Mince-meat (home-made)

Pies

Prunes (dried )

Raisins

Sandwiches

Sardines (canned)

Salt mackerel

159 to 20.3
14.4 to 27.8

15.0
10. o

5.0
22.9

8.6 to

47.4 1

35.3

28.4 to 48.0

13.8

II. 6 to 25. 0

40.1 to 43.6

38.0 to 44-9

27.7

1 . 2 to 2 . s
9.2

6.5 to 10. 1
19

2 . 6 to 5 . 7
13.7 to 14.5
II. 4 to 12.9

6.7
4

• One Calorie equals looo calories.

FOOD IN RELATION TO HUMAN LIFE

119

COMPOSITION OF SOME COMMON FOOD MATERIALS. - Con/.n««/

V. Fuel Value 500-icxx) Calories per Pound

Food-material.

Beef (round)

Beef (sirloin steak).
Chicken (fowls) . . . .

Cream

Eggs

Herring (smoked). .

Meats (lean)

Olives

Salmon (fresh)

Salmon (canned)...
Tapioca pudding. . .

Tongue (beef)

Turkey

Veal (breast)

Refuse.

Per cent.

8.5

12.8

18.0 to 42.7

II. 2

44 4
0.5 to II. 3

19.0
23.8 to 35.1
1 1. 7 to 16.9

9.2 to 55-3
17.1 to 32.4
15.7 to 25.4

Water.

Per cent.

62. s

54-0

38.31053.7

74.0

65 5

19 2

59.9 to 69.2

52.4

45 otosi 2

54 6 to 58 . 2

52.0 to 71.6

32.4 to 69.2

41. 1 to 44-7

48.51055-7

Nitroge-
nous
Substances

Per cent.
19.2
16. 5

11. 5 to 16.0

2.5

II. 9

20.5

18. 1 to 21.4
14

12.6 to 15- o
18.6 to 20.2

2.8 to 4.2
7.8 to 20.2
15.8 to 16.8

14.2 to 16.9

Fat.

Per cent
9.2
16. 1
6.9 to 21.5
18. 5
9 3
8.8
7.8 to 14.2

21.0
6.6to 9.5
5.6to 9.8

2.3 to 4 8
0.7 to IS. 3
5.91025.5

9.4 to 12.8

VI. Fuel Value 4oo-5cx3 Calories per Pound

Beans (canned red kidney) .

Calf's-foot jelly

Salt cod (boneless)

Succotash (canned)

Sweet potatoes

1.6

72.7
77.6
54.8
71.4 to 79.9
55-2

7.0

4.3

27.7

2.9 to 4.4

1.4

0.3

0.7 to 1.7

0.6

VII. Fuel Value 300-400 Calories per Pound

Bananas

Butter beans.
Fish (fresh)..

Grapes

Hash

Milk

Potatoes

35 o I 48.9
50.0 I 29.4
25.2 to 46.0 46.1 to 49. 1
S8.o
80.3
87.0
62.6

08
4.7
II. 9 to 12.0
1.0
6.0
3 3

0.4
0.3
1.8 to5.9
1.2
19
4.0

Carbo-
hydrates.

Per cent.

4-5

3 5
21.9 to ;^.i

18.5
17 4

14.9 to 22.4
21.9

14 3
14 6

14.4
9 4

SO
14.7

VIII. Fuel Value 200-300 Calories per Pound

Apples

Chicken (broilers).

Cranberries

Onions

Oysters (.solid). . . .

Parsnips

Pears

25.0
31.4 to 55.

20.0
10.0

63.3
44-6 to 52.4
87.6 to 89.5

78.9
82.2 to 92.4

66.4

76.2

0.3
9.0 to IS. 7
0.4 to 0.5

1.4
4 5 to7 3

0.3
I.I to 1.8
0.4 to 0.9

0.3
0.5 to 1.8

0.4

10.8

9.3 to 10.9
8.9

I 5 to 6.2
10.8
12.7

IX. Fuel Value 100-200 Calories per Pound

Beets

Cabbage

Carrots

Green corn

Lemons

Oranges

Soups (canned)

Spinach

Squash

Tomatoes (canned).

20.0
15 o
20.0
61.0
30.0
27.0

0 to 92.8

6 to 92.8

44.2

5 to

97-9 1

13
14
0.9

1.2

0.7

0.6
2.9 to SO
1.8 to 2.4

0.7
0.3 to 1.7

0.4
0.5

0.1
0.2 to 0.8
0.2 to 0.5

0.2

O.I to 0.3

7.7
48

7 4
7-7
5 9
8.5
0.6 tos 7
31 t03.4

4 5
1.4 to 8.1

X. Fuel Value io-ioo Calories per Pound

Asparagus

Bouillon (canned)
Celery
Cucumbers
Watermelons

94.0
96.5 to 96.7
75.6
81. 1
37.5

1.8
.7 to 2.6
09
0.7
0.2

0.2

0.0 to o.

0.2
O.I

3-3
. I to 0.3
26
2.6

3.1

I20 AIR, WATER, AND FOOD

complete nutrition. The nutritive ratio, or the proportion of
nitrogenous to non-nitrogenous food, must be maintained in the
proportion of i to 3, or at least i to 5.

The preceding table of one hundred common food-materials
is arranged in the order of calorific or energy-giving power, but
in considering the food value of any one substance its nitro-
gen content must also be considered, and such combinations
made as will yield the requisite elements for a well-balanced
ration.

From even a cursory examination of the table it will be seen
how widely some of the foodstuffs differ under differing con-
ditions of soil moisture, fertilization in the case of plants, and
of fatness or leanness in animals, of method of preparation or of
combination in cooked foods.

Therefore examinations of materials are imperative if there is
to be any basis of calculation. In an institution where, for
instance, flour forms two-thirds of the daily ration, if it con-
tains the lowest per cent of nitrogen it may not furnish sufficient
proteid for a well-balanced ration, or if the meat used is very
lean there may not be fat enough for the best nutrition.

The great variation in the proportion of water leads to many
surprises, and the amount of unedible material is to be con-
sidered. The uneducated provider buys oysters under the
impression that he is furnishing food of high value, and does
not distinguish between potatoes and rice.

In the present state of our knowledge, the best use to which
we can put such tables and analyses is as a check against gross
errors of diet, which are found with alarming frequency espe-
cially among children and students, those who can least afford to
make them. References will be found in the Bibliography to
works for further study along these lines.

Dietaries. — A dietary is simply a known amount of food of
known composition per person per day, week, or month.

What is called a standard dietary is such a combination of
food-materials as shall furnish the amounts held to be neces-
sary. The following are examples of such standard dietaries:

FOOD IN RELATION TO HUMAN LIFE

121

Approximate amounts
required daily by

Nitrogenous,
grams.

Fats,
grams.

Carbohydrates,
grams.

Calories.

Child of 6-9

Child of 9-14

Adult at rest

100

125

45
45
75
90
125

200
281
380

450
500

1593
1890
2665

Adult at moderate work. .
Adult at hard work

3092
3725

(In feeding experiments from 10 to 20 per cent more must be allowed for waste
and indigestibility.)

From the table on page ii8 may be selected such food as will
give the required quantities in variety enough to suit any taste.
That which the table cannot give is the per cent of each which,
under any given condition, will be utilized by the person fed.
The strength of the digestive juices, exercise, fresh air, the
cooking, the mixing of the foods, the habits of mind as to food,
the customs of the family, all influence this utilization, so that
other means must be restored to in order to gain an idea of
what is practicable. This is done by taking account of the food
of persons free to choose; of those in different countries, in
different circumstances, and using a great variety of materials.
Since Voit made his standard dietary in 1870, many hundreds,
at least, have been so gathered in the United States alone —
more than two hundred since 1886. All the information thus
gained goes to confirm the theoretical standard, and also to
show how much depends upon suitable preparation and com-
bination. These last two things help each other.

As food is ordinarily prepared, about 10 per cent must be
deducted for indigestibiHty in a customary mixed diet, and
about 10 per cent more for the refuse or waste of food as pur-
chased, so that of the total pounds of meat, vegetables, and
groceries some 20 per cent is of no final service in the body. It
is immaterial whether this amount is subtracted from the final
calculation or whether the higher figures be taken, that is,
whether 125 grams of proteid as purchased or 100 grams final
utility is used. There will be an unknown limit in either case.
According to late experiments 100 grams of proteid is high.

122 AIR, WATER, AND FOOD

The waste of fats is less in proportion as the dietary is a restricted
one.

Knowledge of Food Values Necessary. — The most serious
aspect of the food question is that the taking of it is voluntary,
not, like air, a necessity beyond control, and that the most
fantastic ideas are allowed to rule. The day-laborer is in Httle
danger, since his food demand is made strong by out-of-door
exercise; but the student who shuts himself up in hot, close
rooms, and who does not look upon food as his capital, but only
as a disagreeable task or an amusement, is in great danger, as
is he who, having heard that one can live on a few cents a day,
proceeds to try it without knowledge, and suffers a loss of effi-
ciency for years or for all his Hfe.

It is not nearly so difficult to acquire a working knowledge
of food values as of whist or golf, so that on entering a restaurant
a suitable menu may be made up within one's allowance. It
is only necessary to correct prevailing impressions and rein-
force one's experience.

Figs, dates, raisins and prunes are apt to be regarded as
luxuries instead of as rich food-substances of a most digestible
kind when freed from skin and seed. Nuts are a much neg-
lected form of wholesome food, admirably suited to a winter
table from their richness in fat, and also furnishing muscular
energy, as is seen in the agile squirrel, and is proved by many
human examples. With nuts, however, must be taken fruits
or other bulky foods, to balance the concentration. The some-
what compact and oily substance must be finely divided and
freed from its astringent skin.

In distinction from these rich foodstuffs, we find oranges,
apples, etc.; the usual garden vegetables, asparagus, lettuce,
etc., which while they fill an important place in the dietary,
add little directly to the energy of the body and need not be
considered except as, by their flavor or aesthetic stimulus, they
add to the efficiency of the rest.

The foods which furnish the greatest nutrition for the least
money are such materials as corn meal, wheat flour, milk,

FOOD IN RELATION TO HUMAN LIFE 123

beans, cheese and sugar. The expensive cuts of meat, high-
priced breakfast cereals and the Uke, add but Httle to the nu-
tritive value but greatly increase the cost of living. A meal of
lettuce dressed with oil, eaten with bread and cheese, fulfils all the
requirements of nutrition, and may cost five cents. The same
food value from sweet breads, grape-fruit, etc., might cost a
dollar. Incorrect ideas in regard to food values, and prejudice
inherited or acquired against certain foods, have too often
resulted in excluding wholesome and nutritious articles from
the dietary and decreasing thereby the efficiency of the human
machine.

CHAPTER VIII

THE PROBLEM OF SAFE FOOD. ADULTERATION AND
SOPHISTICATION

Adulteration grows largely, if not almost entirely, from ex-
cessive competition. Nearly every article of common food has
been found at one time or another to be adulterated, yet manu-
facturers testify that they wihingly would stop this addition of
foreign material if they could be sure that their competitors
would stop also. Other causes there are also: demands for
goods out of season; for perishable products which must come
many miles; the failure of the supply of a given substance to
meet a continuing demand; all of these lead to adulteration,
imitation and substitution.

To many people otherwise intelligent, the term adulterated food
is synonymous with poisoned food. With others, thanks to
alarming newspaper articles, not wholly disinterested, the general
impression is far beyond the reality. It is not necessary to
use poisonous or even deleterious material; it needs only to mix
with the food material some substance cheaper but harmless,
to make some change in the outward appearance of the article
so that people shall not recognize the familiar substance, and
then to herald far and wide the discovery of a new process by
which the food value is greatly enhanced. "Things are not
what they seem" is nowhere more true than in the case of
foods.

Definition of Adulteration. — To adulterate is "to debase,^'' "to
make impure by an admixture of baser materials." The word
"adulterated " refers to any food to which any foreign substance,
not a proper portion of the food, has been added. It does not
matter whether the added material is of greater value than the
food itself. The addition of coffee to cereal or substitute coffees,

124

ADULTERATION AND SOPHISTICATION 125

is properly held to be an adulteration. Deterioration should not
be mistaken for adulteration. People who are not wholly familiar
with the appearance of a food or the chemical and physical
changes which it may undergo, think that if it does not taste just
right or look just right that it must be adulterated. Appearance
has slight relation to the purity of the article in these days of
paint, polish and powder.

Some forms of adulteration are more properly described under
the head of misbranding, that is, referring to foods incorrectly de-
scribed by the label. WTiilc the significance is not exactly the
same as that of the word adulterated, yet the two may sometimes
be applied to the same product. For instance, the addition of
starch to sausage to conceal the use of excessive amounts of water
and of fat constitutes an adulteration, which would not be the case
if the article were properly branded to show the presence of the
added ''filler."

To adulterate the coin of the realm or the liquor of the bar with
a baser metal or an imitation whisky is a heinous offence. So is
the mixture of milk with the baser article, water, which thereby
lowers its food value. But the "wretched sophistry" which ob-
scures the nature of things on a package of prepared food mis-
leads more persons and inflicts more injury upon the community
than the other, yet goes unrebuked. The most barefaced asser-
tions are printed in magazines, and "pure-food shows" only whet
the appetite for something new.

Legal Definition of Adulteration and Misbranding. — In the
Federal Pure Food Law, commonly known as the Food and Drugs
Act of June 30, 1906, adulteration and misbranding are thus
defined :

Sec. 7. That for the purposes of this Act an article shall be
deemed to be adulterated:

In the case of food :

First. If any substance has been mixed and packed with it so
as to reduce or lower or injuriously affect its quality or strength.

Second. If any substance has been substituted wholh- or
in part for the article.

126 AIR, WATER, AND FOOD

Third. If any valuable constituent of the article has been
wholly or in part abstracted.

Fourth. If it be mixed, colored, powdered, coated, or stained
in a manner whereby damage or inferiority is concealed.

Fifth. If it contains any added poisonous or other added dele-
terious ingredient which may render such articles injurious to
health : Provided, That when in the preparation of food products
for shipment they are preserved by any external application ap-
plied in such manner that the preservative is necessarily removed
mechanically, or by maceration in water, or otherwise, and direc-
tions for the removal of said preservative shall be printed on the
covering or the package, the provisions of this Act shall be con-
strued as applying only when said products are ready for con-
sumption.

Sixth. If it consists in whole or in part of a filthy, decomposed,
or putrid animal or vegetable substance, or any portion of an
animal unfit for food, whether manufactured or not, or if it is the
product of a diseased animal, or one that has died otherwise than
by slaughter.

Sec. 8. That the term "misbranded," as used herein, shall
apply to all drugs, or articles of food, or articles which enter into
the composition of food, the package or label of which shall bear
any statement, design, or device regarding such article, or the
ingredients or substances contained therein which shall be false or
misleading in any particular, and to any food or drug product
which is falsely branded as to the State, Territory, or country in
which it is manufactured or produced.

That for the purposes of this Act an article shall also be deemed
to be misbranded:

In the case of food :

First. If it be an imitation of or offered for sale under the dis-
tinctive name of another article.

Second. If it be labeled or branded so as to deceive or mislead
the purchaser, or purport to be a foreign product when not so,
or if the contents of the package as originally put up shall have
been removed, in whole or in part, and other contents shall have

ADULTERATION AND SOPHISTICATION 127

been placed in such package, or if it fail to bear a statement on
the label of the c|uantity or proportion of any morphine, opium,
cocaine, heroin, alpha or beta eucaine, chloroform, cannabis
indica, chloral hydrate, or acetanilide, or any derivative or prep-
aration of any such substances contained therein.

Third. If in package form, and the contents are stated in terms
of weight or measure, they are not plainly and correctly stated on
the outside of the package.

Fourth. If the package containing it or its label shall bear any
statement, design, or device regarding the ingredients or the sub-
stances contained therein, which statement, design, or device shall
be false or misleading in any particular : Provided, That an article
of food which does not contain any added poisonous or deleterious
ingredients shall not be deemed to be adulterated or misbranded
in the following cases :

First. In the case of mixtures or compounds which may be
now or from time to time hereafter knowTi as articles of food,
under their own distinctive names, and not an imitation of or
offered for sale under the distinctive name of another article, if
the name be accompanied on the same label or brand with a state-
ment of the place where said article has been manufactured or
produced.

Second. In the case of articles labeled, branded, or tagged
so as to plainly indicate that they are compounds, imitations,
or blends, and the word "compound," "imitation," or "blend,"
as the case may be, is plainly stated on the package in which
it is offered for sale: Provided, That the term blend as used
herein shall be construed to mean a mkture of like substances,
not excluding harmless coloring or flavoring ingredients used
for the purpose of coloring and flavoring only: And provided
Jtiriher, That nothing in this act shall be construed as requir-
ing or compelling proprietors or manufacturers of proprietary
foods which contain no unwholesome added mgredient to dis-
close their trade formulas, except in so far as the provisions of
this act may require to secure freedom from adulteration or
misbranding.

128 AIR, WATER, AND FOOD

Extent of Adulteration. — In any discussion of the extent to
which adulterated foods are sold it must be borne in mind that
the adulterated articles make up only a relatively small propor-
tion of the food that actually passes over the counter. Flour, for
example, is seldom adulterated; pepper, mustard and vanilla ex-
tract often are. For one pound of these substances sold, looo
pounds or more of flour go out from the store. Figures given in
official reports of food inspection do not represent the case exactly,
because the inspectors are trained men, and purchase samples of
those lines of goods which experience has shown them to be most
likely to be adulterated. Brands of foods which they have reason
to believe are pure they do not sample. Estimated on the total
quantity sold, it is doubtful if more than 5 to 10 per cent of the
food sold is adulterated in any way, and these figures would un-
doubtedly be much too high for those states in which there is a
well-enforced system of food inspection.

Character of Adulteration. — Much of the present propaganda
in the interests of pure food and the movement for the protection
of the consumer can be summed up in three words: "An Honest
Label." In many cases an accurate and true statement of the
contents of the can or package is the only protection needed by
the consumer, and is fully as efhcient as well as much cheaper
than prosecutions or restrictive measures. Many of the terms
used on food packages deceive only the ignorant purchaser.
"Strictly pure" is a well-understood trade term, with a meaning
known to the initiated; the words "Home-Made" may cover
some of the most highly developed products of synthetic organic
chemistry.

The cases in which the adulteration is of a character dele-
terious to health are fortunately few. The use of canned goods
brings certain dangers in the dissolved metals from the cans or
from the solder, also from a careless habit of allowing foods
to stand in the opened tins. The liking for bright green pickles
and peas leads to coloration by copper salts.

So rapidly do new substances come upon the market that it is
of little use to put into a general text-book definite statements of

ADULTERATION AND SOPHISTICATION 1 29

the quality of many foods. A baking-powder or a spice which is
honestly made to-day may next week pass into the hands of un-
scrupulous dealers who please the public and thereby salve their
consciences.

To furnish what the people think they want has been the rule
from the days of an earlier generation of grocers, who divided a
barrel of cooking-soda in halves and set one-half on one side of
the store for "saleratus" and the other on the opposite side for
soda, so that there should be no suspicion in the mind of the cus-
tomer that the packages came from the same barrel, and yet each
might satisfy his individual preference.

Names that have passed down from a former generation as
being above reproach are now found to cover adulterated goods.
The trademark has passed into other and less scrupulous hands,
and the new owners do not hesitate to trade upon the reputation
earned by their predecessors. There are, however, several phases
of the subject that should be briefly mentioned.

Breakfast Foods. — The craving for something new to stimulate
a jaded appetite already spoiled by endless variety and bad com-
binations has led to the manufacture of a cereal preparation for
nearly every day in the year, regarding some of which the state-
ment is made that they are ''predigested." No better commen-
tary on the laziness or wilful ignorance of American providers
could be made than this. Little do the people know about wheat
or cooking if they suppose that grain can be changed by manipu-
lation in any kind of machine so as to give greater food value than
was contained in the grain. WTiile it is true that some of these
preparations are far better than the half-cooked grains found on
so many tables, the fact remains that it is the cook and not the
substance which is poor. The false statements on food packages
of all kinds are so absurd that they would defeat their own pur-
pose were they viewed in the light of common sense. It is not
always best to have food which is too easily digested.

A predigested food is quickly absorbed into the circulation,
and hence a small quantity causes a sensation of fulness and satis-
faction, which, however, soon passes away and a faintness results.

130 AIR, WATER, AND FOOD

This is especially true of the sugars and dextrins. Frequent
meals should go with easily absorbed foods. The rapid digestion
is the cause of much pernicious eating of sweets between meals,
which satisfies the appetite for the time being and prevents sub-
stantial quantities of other foods being taken at the time they
are offered.

From a study of analyses of a large number of foods the fol-
lowing conclusions are drawn by F. W. Robison: *

1. The breakfast foods are legitimate and valuable foods.

2. Predigestion has been carried on in the majority of them
to a limited degree only.

3. The price for which they are sold is as a rule excessive and
not in keeping with their nutritive values.

4. They contain, as a rule, considerable fibre which, while
probably rendering them less digestible, at the same time, may
render them more wholesome to the average person.

5. The claims made for many of them are not warranted by
the facts.

6. The claim that they are far more nutritious than the wheat
and grains from which they are made is not substantiated.

7. They are palatable as a rule and pleasing to the eye.

8. The digestibility of these products as compared with highly
milled goods, while probably favorable to the latter, does not give
due credit to the former, because of the healthful influence of the
fibre and mineral matter in the breakfast foods.

9. Rolled oats or oatmeal as a source of protein and of fuel is
ahead of the wheat preparations, excepting of course the special
gluten foods, which are manifestly in a different class.

In general, the cost of these foods is low if they are considered
merely as confections to please the taste, but they are expensive
foods regarded as substitutes for the ordinary cereal products.

This is well shown in the following table in which the fuel
value of breakfast foods and other common food products ob-
tained for a given sum is graphically compared.

* Mich. Agr. Expt. Sta., Bull., 211 (1904).

ADULTERATION AND SOPHISTICATION

131

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132 AIR, WATER, AND FOOD

Colors and Preservatives in Food. — For many years such sub-
stances as alcohol, vinegar, sugar, salt, and the like, have been
used to preserve food. Such materials are commonly held to be
harmless to persons of sound digestion if used in moderate
amounts. Within recent years, however, there has been a con-
stantly increasing tendency toward the use in food products of
such powerful antiseptics as formaldehyde, salicylic and benzoic
acids and their salts, and boric acid. An important distinction
to be borne in mind between this class of preservatives and those
first named is that the former when used in food in quantity suffi-
cient to preserve it make their presence known to the consumer
by either their taste or odor. With the chemical preservatives,
however, an intimation of their presence is conveyed to the con-
sumer only by a statement on the label. It is the general feeling
among those engaged in the enforcement of the food laws that
the common use of these preservatives should be forbidden, or
that they should be allowed only under certain definite restric-
tions. The question is not one of their possible harmful effect
only, although it cannot be successfully denied that their unre-
stricted use would lead to grave danger to health, especially in the
case of invalids and children, or those with various degrees of
digestive efficiency. It seems reasonable to infer that the proc-
esses of digestion, being largely the result of bacterial and
enzymic action, will be retarded or interfered with to a greater
or less extent by substances which inhibit bacterial action in
food.

There is, however, another reason for objecting to the use of
chemical preservatives. By their use much food that is unwhole-
some and unfit for consumption can be, and is, placed upon the
market with no warning to the consumer. ''The man who adds
formaldehyde to his milk takes down the danger signal, but does
not remove the danger."

Similarly, objections can be made to the use of coal-tar colors
in foods. There are hundreds of food packages which would
never leave the grocers' shelves were it not for the fact that by
the use of artificial color their true composition and the actual

ADULTERATION AND SOPHISTICATION 133

nature of the materials from which they are made is hidden.
Apart from any question as to the harmfulness of these dyes
there is ample reason for their use being strictly regulated by
official action, in that their use except under such supervision
allows the manufacturer to sell inferior articles under the appear-
ance of standard foods; it permits the customer to be misled as
to the strength and purity of the product that he buys; the age
and past history of the product may be made a sealed book;
finally, by the use of coloring, an unwholesome and improper
food may be put upon the market.

Summary. — The chief dangers in food are from wrong pro-
portions of proteid, fat, and carbohydrates, from fermentable and
irritating decompositions, from bad methods of cooking and
unsuitable combinations, from transmission of micro-organisms
either by exposure to dust or by contact with filthy hands or ves-
sels, to a favorable medium for the growth of pathogenic germs,
from unsuitable food scientifically disguised.

From this hasty survey it will be seen how little danger to
health is incurred if only reasonable care is taken and if the always
doubtful articles are avoided.

Take, for instance, that most commonly adulterated class,
spices. Who will say that it may not be better to eat corn and
buckwheat and ground peas than pure pepper? Rice is certainly
a more wholesome food than ginger, and starch than soda. Glu-
cose is even more easily absorbed than cane-sugar. These are
cases of frauds on the pockets, but possibly blessings in disguise
for the stomachs. When any community is so ignorant as to per-
mit of such glaring cases of adulteration as coal-tar dyes in food,
and gypsum in cream of tartar, they deserve to suffer. It is
knowledge on the part of each intelligent citizen which will mend
matters, even if it is only that kind of empirical knowledge that
one is forced to learn in relation to electricity and steam in order
to live in a modern house.

This knowledge is now easily obtained through the city, state
and governmental laboratories, and their publications are acces-
sible to all who can read and write. There is therefore no excuse

134 AIR, WATER, AND FOOD

for general ignorance and credulity as to trade preparations of
foods, any more than for the degrading habit of purchasing patent
medicines to remedy the ills caused by the misuse of food. Both
together form the saddest commentary on human weakness and
lack of rational thought.

CHAPTER IX

ANALYTICAL METHODS

In the discussion of the methods employed for the examination
of food-materials, only a few typical substances have been con-
sidered, and the processes given are such as to bring into promi-
nence the scientific aspect rather than the technical detail of the
subject; at the same time it is hoped that a sufficient variety of
methods is given to enable the student to gain considerable expe-
rience in the necessarily short time which can be alloted to the
subject.

Both on account of its importance as a food-material and
on account of its availability for the various tests, milk has been
chosen as a type of animal food; moreover, it may be made to
serve as an excellent example of the changes to which food-ma-
terials are liable through the growth of the micro-organisms.
The analysis of milk includes determinations of specific gravity,
water, or total solids, ash, fat, proteids and sugar, the separation
of casein and albumin, and the detection of preservatives, color-
ing matters, and added water.

The breakfast cereals are taken as typical of vegetable foods.
The examination which may be made of this class includes the
determination of moisture, ash, fat, nitrogen and proteids,
starch, cellulose, and the products of peptonization and sacchari-
fication.

The nature and composition of the various fats and oils is
briefly illustrated by the examination of butter and the deter-
mination of the principal " constants " of the butter-fat.

The results of fermentation are illustrated by the deter-
mination of alcohol in beer, wine, meat extracts, patent medi-
cines and "temperance drinks," flavoring essences and the like.
The determination of the relative proportion of volatile and

135

136

AIR, WATER, AND FOOD

fixed acids, of the saccharine products of malting, and of volatile
oils or flavoring principles, is also instructive.

A more elaborate discussion of the methods used in food
analysis and of the interpretation of results will be found in
the larger works upon the subject. As reference books for the
use of the student in the laboratory, the following, in the author's
experience, have been found especially helpful: Leach: Food
Inspection and Analysis; Sherman: Organic Analysis; Rolfe:
The Polariscope in the Laboratory; Bulletin 107, Bureau of
Chemistry.

MILK

Milk is a food material of somewhat complex and variable
composition but can be described as essentially an aqueous
solution of milk sugar, mineral salts and soluble albumin con-
taining suspended globules of fat and partially dissolved casein.

General Composition. — In approximate figures the average
percentage composition of milk may be stated :

Per cent

Total solids 12.8

Fat 3-8

Protein 3.6

Ash 0.7

Milk sugar 4.7

Solids not fat 9.0

From these figures there may be in normal milk quite decided
variations and figures have been reported which differ widely
from them, some of the discrepancies of the older analyses being
undoubtedly due to the imperfect methods of analysis employed.

Lythgoe * states that all milk completely drawn from healthy
cows will fall between the following limits :

Extreme limits,
per cent.

Usual limits,
per cent.

Herd milk,
per cent.

Total solids. .

Fat

Protein

Ash

Milk sugar. . .
Solids not fat.

10. 0-17.0
2.2- 9.0
2.1- 8.5
0.6- 0.9
4.0- 6.0
7.5-11.0

5-16.0
8- 7.0

5- 4-5
7- 0.8

2-5-5
7-10.0

I I. 8-15.0
3.2- 6.0
2.5- 4.0
0.7- 0.8

4-3- 5-3
8.0- 9.5

* Bull. Mass. Slate Bd. Health, 1910, p. 419.

ANALYTICAL METHODS

137

Variations in Composition. — Besides variations in compo-
sition which may be due to individual cows there are also certain
well-established differences due to environment or to racial influ-
ences. Among the more important of these are:

(i) The Breed of the Cow. — Some breeds yield quantity,
others quality. The Jersey and Guernsey cattle, for instance,
give comparatively small quantities of milk rich in fat; the
Holstein cows, on the other hand, yield much larger amounts of
milk of decidedly lower solids and fat content. These differ-
ences are well simimarized in the following table based on data
collected by the Massachusetts Board of Health.*

Breed.

Jersey

Guernsey. .
Ayrshire. . .
Dutch Belt
Holstein. . .

Specific
gravity.

Total

Fat,

Protein,

Ash,

Solids

solids,

per

not fat,

per cent.

cent.

per cent.

I 034

14-57

5-40

3-54

0.78

9.17

I 034

14.40

5.00

3-77

0.77

9.40

1.032

12.57

4.00

2.90

0.77

8.57

1.032

12.03

3.60

2.62

0.68

8.43

1.032

II .96

3-35

2.99

0.69

8.61

Milk

sugar,

per cent.

If individual differences are eliminated and only fully drawn
mixed milk from herds is considered, the variation due to breed
is the factor of the greatest influence in permanently affecting
the composition of milk.

(2) The Time of Year. — The poorest milk is produced during
the spring and early summer months, the richest during the
seasons of autumn and early winter, when the cattle are getting
a smaller proportion of green feed. This difference is clearly
shown in the following table f which gives the seasonal average
for 16 years:

Total solids,
per cent.

Fat.
per cent.

Solids not fat,
per cent.

Nov .—Jan

13 04
12.72
12.66
13 03

4. II
3-88
389
4-25

8.93
8.84
8.77
8.78

Feb. -Apr

May — Aug

Oct. -Nov

* Bur. of Chan., Bull. 132, p. 129.

t Richmond: Dairy Chemistry, p. 126.

138

AIR, WATER, AND FOOD

This variation in composition of milk between the pasture-fed
and the stall-fed season has in the past received legal recognition
in the fixing of milk standards. In Massachusetts for many
years the legal standard for total solids was set at 13 per cent
in the winter months and at 12 per cent in the summer season.

(3) Time of Day. — Milk which has been drawn in the even-
ing is nearly always richer in fat than the morning milk as shown
in the following averages:

Morning milk.
Evening milk.

Specific
gravity.

.0322
.0318

Total solids.

12.53
12.94

Fat.

4.04

(4) "Fore" milk vs. "strip pings. '^ — If different portions of
the whole quantity of milk obtained at a single milking are ex-
amined separately they will be found to show marked differences
in fat content, especially as between the first and last portions.
The other constituents of the milk do not vary so greatly as
the fat. The first portions of milk, the "fore" milk, contain
much less fat than do the last portions or "strippings." The
following figures, due to Van Slyke, illustrate this point:

Per cent of fat in milk.

Cow I.

Cow 2.

Cow 3.

First portion drawn

Second portion drawn

Third portion drawn

Fourth portion drawn (strippings) .

0.90
2.60

5-35
9.80

1.60
3.20
4. 10
8.10

1.60

3-25
5.00
8.30

This difference in composition is explained by the separation
of the milk while in the udder of the cow, cream rising to the
top just as would happen if the milk stood in a vessel, hence
being drawn last. Dishonest dairymen have in the past taken
advantage of this fact in adulteration cases, by having the cows
partially milked in the presence of unsuspecting witnesses, the
resulting "known purity" milk being thus largely "fore" milk.

ANALYTICAL METHODS 139

In general it will be found that to whatever causes the varia-
tions noted in the composition of milk are due, the differences
are shown much more in the fat than in any other constituent.
The protein is also variable, although to a somewhat less extent,
and the milk sugar and ash are much more nearly constant.

METHODS OF ANALYSIS

Preparation of the Sample. — • Since the cream will rise on a
sample of milk sufficiently in five minutes to destroy the uni-
formity of the sample, great care must be used in taking a portion
for analysis to ensure that it represents a fair average of the
milk. The best way is to pour the milk from the containing
vessel into another and back again several times, or if this is
impracticable it should be thoroughly stirred before being sam-
pled. If the analytical sample has stood for any appreciable
time it should be mixed by pouring back and forth before a
portion is removed to test, otherwise concordant results cannot
be obtained. Do not shake the sample since this tends toward
a separation of the fat.

Specific Gravity. — This is usually taken with a special form
of hydrometer, known as a lactometer. The Quevenne lactom-
eter has a scale graduated into 25 equal parts, extending from
15 to 40, corresponding to specific gravities from 1.015 to 1.040.
The best form of instrument is that provided with a thermometer.

The lactometer is graduated to give correct results at 60° F.
(15.6° C.) and the reading should be made at approximately
that temperature, between 55 and 65 degrees, and then corrected
to standard temperature. This may be done by adding o.i
to the reading for each degree F. above 60° F., or subtracting
0.1 for each degree F. below 60° F. If the temperature is
read in Centigrade degrees the correction may be made by the
table on page 216.

The New York Board of Health lactometer has a scale reading
o in water, and 100 in milk with a specific gravity of 1.029, which
is taken as the lowest limit for pure milk. The instrument is
used in the same manner as the Quevenne lactometer and the

I40 AIR, WATER, AND FOOD

readings can readily be converted into degrees of the latter
instrument.

Notes. — The specific gravity of milk fat is about 0.93 ; of tjie
soHds not fat approximately 1.5. The specific gravity of the
milk itself is thus a function of the two; the former lowers it,
the latter increases it. As would be expected from the variable
composition of milk, the specific gravity is also a variable. The
values for normal milk from a herd, however, will usually fall
between 1.030 and 1.034.

Taken by itself the specific gravity is of Uttle value in showing
adulteration. The addition of water lowers the specific gravity
of milk; the removal of cream raises it, this being the lighter
portion of the milk. It is therefore theoretically possible by
skilful manipulation to both skim and water a sample and still
have its specific gravity correspond to that of normal milk.
Such a sample would, however, be readily recognized by one
familiar with the appearance of the genuine product.

The lactometer reading is of value in rapid analysis of milk
for calculating the soHds in connection with the Babcock method
of fat determination (see page 148).

Total Solids. — Use a platinum dish having a flat bottom
about 2I inches in diameter. Ignite and weigh the dish accu-
rately, then add about 5.1 grams to the weights on the balance-
pan. With a pipette dehver 5 c.c. of the well-mixed milk into
the dish and weigh the whole as rapidly as possible to the nearest
milHgram. Evaporate the milk to dryness on the water-bath
and then dry it in the oven at 100° C. to constant weight. Three
hours drying is usually sufficient.

Notes. — It is important that the milk should be dried in a
thin layer, so that the removal of the water shall take place as
quickly as possible. Under these conditions the residue ob-
tained is nearly white, but if the process be prolonged, it may
have a brownish color from the caramelization of the sugar.

If it is not desired to determine ash on the same weighed
portion as used for the solids, lead foil dishes or tin blacking
box covers may be used instead of platinum dishes.

Ash. — Ignite the platinum dish containing the residue from

ANALYTICAL METHODS

141

the preceding determination at a low red heat until the ash is
white or of a uniform light gray color. This may be done in a
mufHe furnace at a temperature not exceeding about •600° C,
or over a burner carefully regulated so that the dish is nowhere
heated above the slightest visible redness.

The ash, after weighing, may be tested
for boric acid or carbonates as described
on page 154.

Fat. — (a) Adams' Paper Coil Method.
Roll a strip of fat-free blotting paper *
about 22 inches long and 2^ inches wide,
into a loose coil and fasten it by a bit
of wire. Hold the coil in one hand and
slowly run on to the upper end of it ex-
actly 5 c.c. of milk from a pipette. If
preferred, about 5 grams of milk may
be weighed quickly in a small beaker,
and one end of the coil introduced so as
to absorb the milk, care being taken to
absorb it as nearly completely as possible.
The beaker is then quickly re-weighed.

Place the coil, after charging with the
milk, dry end downward, in the water
oven and dry it for two hours, then
extract it for at least two hours in a
Soxhlet extractor as shown in Fig. i
Use about 100 c.c. of either petroleum;
ether or anhydrous ethyl ether and weigh
the flask to the nearest milligram. At
the end of this time disconnect the appa-
ratus when the extractor is nearly full of ether, thus recovering
a large portion of the solvent, and evaporate the remainder
{away from a flame), conveniently by the electric heater, using
suction. Dry the fat to constant weight in the water-oven. In

Fig. II.

* Schleicher and Schiill make suitable strips which can be obtained from dealers
in chemical suppHes, or the strips may be previously prepared in the laboratory
from thick filter paper and e.xtracted with ether before using.

142 AIR, WATER, AND FOOD

drying the extracted fat it may be heated for two hours the
first time, then in one hour periods until the loss of weight is
not over a milligram.

Notes. — The only part of the method due to Adams is the
drying of the milk on porous paper. This is, however, of great
importance since the absorbent paper exercises a selective
action on the constituents of milk so that the fat is left on the
surface of the paper, mixed with only about one-third of the
non-fatty solids, and hence is more easily extracted; further,
owing to the greatly increased surface exposed, the extraction
of the fat is practically complete in a comparatively short time.

Ethyl ether is the solvent commonly employed but care should
be taken that it is anhydrous, otherwise small amounts of milk
sugar will be extracted. For this reason petroleum ether is
to be preferred as a solvent, although its action is considerably
slower than that of the other.

The Adams method is probably the most accurate for fat de-
termination in milk, but in actual practice is not used so much
as the more rapid centrifugal methods.

(b) Babcock Method. — Measure 17.6 c.c. of the milk from a
pipette into the graduated test bottle; add 17.5 c.c. of sulphuric
acid (sp. gr. = 1.825) pouring it in slowly so as to form a layer,
beneath the milk. After the acid has thus been added to all the
bottles mix the milk and acid thoroughly by a rotary motion,
avoiding the spurting of the liquid into the neck of the bottle.
Place the bottles in opposite pockets of the centrifuge in even
numbers and whirl them for five minutes at the proper speed.
The correct speed varies from 1000 revolutions per minute for
a lo-inch wheel to 700 for one of 24 inches diameter. Then re-
move the bottles and add hot water up to the necks, after which
whirl them again for one minute. Again add hot water until
the fat rises nearly to the top of the graduations. Whirl again
for one minute. Then measure the length of the column of fat
by a pair of dividers, the points being placed at the extreme
lunits of the column, the fat being kept warm, if necessary, by
standing the bottles in water at 60° C. If now one point of the

ANALYTICAL METHODS

143

dividers is placed at the o mark of the scale on the bottle used,
the other will indicate the per cent of fat in the milk.

Notes. — Methods based on centrifugal separation of the fat,
of which the Babcock method is the pioneer, are by far the most
rapid and convenient for general use. They have practically re-
placed the more tedious extraction methods and are universally
employed in creameries and milk depots.

When the acid and milk are mixed the mixture becomes hot
and turns dark colored on account of the charring of the milk
sugar. The casein is first precipitated and then dissolved.
The retarding effect of the milk serum solids being thus elimi-
nated, the fat globules are free to collect in a mass.

The fat obtained should be of a clear, golden yellow color, and
distinctly separated from the acid solution beneath it. If the
fat is light-colored or whitish, often with a layer of white par-
ticles beneath it, it generally indicates that the acid is too weak
or that the milk was too cold when the acid was added. A
dark-colored fat with a sub-stratum of black particles indicates
that the acid is too strong. The best results will be obtained
by the use of acid of the strength noted above.

The capacity of the graduated neck of the bottle between the
o and 10 marks is 2 c.c. The specific gravity of warm milk fat
is 0.9, hence 2 c.c. will weigh 1.8 grams or one-tenth of the
weight of 17.6 c.c. of milk (approximately 18 grams). The
measurement of the extreme limits of the column of fat, rather
than to the upper meniscus, is to correct for the small amount of
fat, 0.1 to 0.2 per cent, that remains in the acid solution.

Milk which has been preserved with formaldehyde usually re-
quires a longer time and more vigorous shaking to dissolve the
curd, on account of the hardening action of this preservative on
the coagulated casein. It is often advantageous to stand the
bottles in water at 60° C. for a time before whirling. Samples
containing formaldehyde will usually give a violet color when
the acid is added to the milk.

(c) Gottlieb Method.* — With a pipette place 5 c.c. of milk
in a 50-c.c. glass stoppered cylinder and add the following re-

* Rose: Z. angew. Chem., iSSS, lOO; Gottlieb: LaitJw. Vers. Stat., iSg2, 6.

144

AIR, WATER, AND FOOD

agents, being careful to add them in the order given and to
shake the stoppered cyhnder thoroughly after the addition of
each reagent: i c.c. of ammonia (sp. gr. = 0.96), 5 c.c. of alcohol,
12.5 c.c. of ethyl ether, and 12.5 c.c. of petroleum ether. Let
the cylinder stand until the lower layer is free from bubbles —
several hours if necessary. Transfer the upper layer to a tared
flask by means of an arrangement similar to a wash-bottle,
as shown in Figure 12. Adjust the sliding tube until the end
rests just above the junction of the two lay-
ers, then by gently blowing force out the
upper layer into the flask. Repeat the ex-
traction, using 10 c.c. each of ethyl ether and
petroleum ether and blowing it off into the
flask as before. Distill off the solvent and
dry the residual fat to constant weight in
the water oven. Dissolve the weighed fat
in a Uttle petroleum ether. If a residue
is found, due to a trace of the aqueous layer
which was blown off with the ether, wash it
several times in the flask by careful decanta-
tion with petroleum ether. Finally dry and
weigh the flask and residue and deduct from
the previous weight. The difference is the
weight of purified fat.
Notes. — All of the successful methods for determining the fat
by direct extraction from the milk itself involve the complete or
partial solution of the casein. In the Gottlieb method the
casein, precipitated from the milk in very finely divided form by
the alcohol, is dissolved by the ammonia. The fat is dissolved
by the ethyl ether and the addition of petroleum ether is to
render less soluble the milk sugar or other non-fatty solids
which would be dissolved by ethyl ether alone.

The method, while apphcable to whole milk, is especially
valuable in determining fat in such products as skim milk or
buttermilk which are low in fat. In such cases it is better to
use ID c.c. of milk and double the quantity of reagents.

ANALYTICAL METHODS 145

Milk Sugar. — The sugar in milk is most readily determined
by its reducing action on P'chling's solution.

Munson and Walker Method.* — Directions. — Measure 25
c.c. of milk into a 500-c.c. graduated flask. Add about 400 c.c.
of water, 10 c.c. of copper sulphate solution,! then 35 c.c. of
tenth-normal sodium hydroxide (or an equivalent cjuantity of a
stronger solution) and make up to 500 c.c. Mix thoroughly
and filter through a dry filter.

In a No. 3 beaker mix 25 c.c. of the Fehhng's copper sulphate
solution and 25 c.c. of the alkaline tartrate solution. Add 50
c.c. of the milk sugar solution, prepared as above, cover the
beaker with a watch glass, and heat it upon wire gauze. Reg-
ulate the flame so that boiling shall begin in four minutes, and
continue the boiling for exactly two minutes.

Filter the cuprous oxide without delay through asbestos in
a weighed Gooch crucible, wash it with hot water until free
from alkali, pour out the hot filtrate, then wash with 10 c.c.
of alcohol and, finally, with 10 c.c. of ether. Dry the crucible
for 30 minutes at the temperature of boiling water and weigh.
Find the milligrams of lactose monohydrate corresponding to
the weight of cuprous oxide from Table XII on page 221 and
calculate the percentage present in the milk.

Notes. — Before the lactose can be determined by Fehling's
solution the protein and fat must first be removed. This is
done by the precipitation with copper hydroxide, the fat being
carried down mechanically by the precipitated protein. The
addition of alkali should be such that a slight excess of copper
still remains in solution, since an excess of alkali will prevent
the precipitation of part of the protein. The quantity stated
in the procedure is correct for most milks.

On account of the considerable dilution of the sample, the vol-
ume of the precipitated protein and fat need not be considered.

The general principle upon which all these methods depend

* /. Am. Chem. Soc, igo6, 663; 1907, 541.

t 69.28 grams per liter. The copper sulphate solution used in the Fehling de-
termination may be conveniently employed.

146 AIR, WATER, AND FOOD

is based on the fact that certain sugars, among which is lactose,
have the power of reducing an alkaline solution of copper to a
lower state of oxidation in which copper is separated as cuprous
oxide. The copper salt which is found to give the most dehcate
and reliable reaction is the tartrate. The two solutions which
make up the Fehling's solution are best preserved separately,
and mixed only when wanted for use, as otherwise the reducing
power of the solution is liable to change.

The amount of reduction of the copper salt to the cuprous
oxide is affected by the rate at which the sugar solution is added,
the time and degree of heating, and the strength of the sugar so-
lution; hence the necessity for adopting a definite procedure
and for taking the results from a table determined by exactly
the same procedure for varying amounts of the sugar.

The asbestos which is used should be previously boiled in
nitric acid and then in dilute sodium hydroxide and thoroughly
washed. A layer about a centimeter thick should be used in
the crucible, and a "blank" determination made with the
Fehling's solution should not show a change in weight greater
than one-half milligram. After the precipitated cuprous oxide
has been weighed it may be dissolved in hot dilute nitric acid,
and the asbestos in the crucible washed and dried as described,
when it is again ready for use. Do not remove the asbestos
from the crucible.

Proteins. Determination of Total Protein. — This is best done
by the Kjeldahl method. Weigh 5 grams of milk into a Kjeldahl
flask, add 10 c.c. of concentrated sulphuric acid and three drops
of mercury and carry out the determination as described on
page 182.

The tendency of the alkaline solution to froth during the
distillation, which is especially noticeable with milk, can be
prevented by the addition of a piece of paraffin the size of a pea.
Multiply the per cent of nitrogen by the factor 6.38 to obtain
the per cent of protein.

Separation of Casein and Albumin. — The usual method of
precipitating the casein by acid at a temperature below the

ANALYTICAL METHODS 147

coagulating point of the albumin, while capable of good results,
is tedious and rather unsatisfactory except after considerable
experience. The following volumetric method, devised by
Van Slyke and Bosworth * gives results of almost equal
accuracy, but requires much less time and skill.

Measure 20 c.c. of the well-mixed milk into a 200-c.c. grad-
uated flask and add about 80 c.c. of water. Add i c.c. of phenol-
phthalein solution and tenth-normal sodium hydroxide until a
faint pink color remains throughout the mixture even after con-
siderable shaking. Avoid an excess of alkali.

To the neutralized diluted sample, which should be at a tem-
perature of 18° C. to 24° C, add tenth-normal acetic acid in
.5-c.c. portions, shaking vigorously for a few seconds after each
addition. After thus adding 25 c.c. and shaking, the mixture
is allowed to come to rest. If enough acid has been added, the
casein separates promptly in large, white flakes, and on standing
a short time, the supernatant liquid appears clear, not at all
milky. If the addition of 25 c.c. of acid is insufiicient to sepa-
rate the casein properly, add i c.c. more of acid and shake;
continue this addition of acid i c.c. at a time, until the casein
separates promptly and completely upon standing a short time.
Note the number of c.c. of acid used.

After the casein is completely precipitated make up the mix-
tures to the 200-c.c. mark with water, shake thoroughly and
filter through a dry filter. Filtration should be rapid and the
the filtrate quite clear. If a marked turbidity is apparent in
the filtrate, a new sample should be taken and the process re-
peated, using more acid than before. Titrate 100 c.c. of the
filtrate with tenth-normal sodium hydroxide and phenolphtha-
lein to a pink color which remains throughout the solution for
thirty seconds. Subtracting the number of c.c. of sodium hy-
droxide from one-half the c.c. of tenth-normal acetic acid added
will give the c.c. of acid required to precipitate the casein for

10 c.c. of milk, (i c.c. of— acetic acid = o.II^I^ gms. of

casein.)

* /. Ind. Eng. Clicm., igog, 768.

148 AIR, WATER, AND FOOD

Calculation of Milk Solids. — It has long been recognized that
in normal milk the constituents are present in a fairly constant
ratio. This being true, it should be possible, having deter-
mined two factors, to find a third by calculation, or at least
to show by such calculation a sufficient variation from the
normal to indicate the adulteration of the sample. For ex-
ample, given the lactometer reading and fat, to calculate the
total solids:

L = the lactometer reading,

5 = increase in lactometer reading by i per cent sohds not fat,
/ = decrease in lactometer reading by i per cent fat,
T = total solids,
S = per cent of solids not fat,
F = per cent of fat.

Then L = Ss - Ff,

Since S = T — F

L = {T-F)s-Ff,

whence T = ^ ~^ ^f + F.

The uncertainty of the calculation lies in the values for s and/,
which, on account of the difference in solution densities of the
components of the soHds not fat, are not absolute constants.

Based on the principle just stated, various formulae have
been proposed for the calculation of milk solids. One of the
simplest of these is that of Hehner and Richmond *

T = — h 1.2F + 0.14,
4

where T is the per cent of total solids, L the reading of the lac-
tometer, and F the fat.

When a number of calculations are to be made, Richmond's
"Milk Scale" will be found convenient. This is an instrument
based on the principle of the slide-rule, having three scales,
two of which, for the fat and the total soUds, are marked on

* Analyst, 1888, 26; i8g2, 170.

ANALYTICAL METHODS

149

the body of the rule, while that for the lactometer readings
is marked on the sliding part.

A similar relation has been worked out for the protein, so
that if a constant value be assumed for the ash, the composition
of a sample may be determined with a fair degree of approxima-
tion from the two simple determinations of specific gravity and
Babcock test.

The relation between the protein and fat has been expressed
by Van Slyke* as P = 0.4 (F - 3) + 2.8. Similarly Olsen f
has proposed the following formula for calculating the protein
from the total solids (T.S.) :

T.S.
1-34

P = T.S. -

These values will naturally be most nearly correct in the case
of normal average milk. With watered or skimmed milk they
will be only approximate.

In the table below the values calculated for a sample are com-
pared with those actually determined:

Determination.

Calculated values.

Lactometer reading

Fat (Babcock)

Total solids

Ash

Proteins

Milk sugar

Solids not fat

12-95

0.7 (assumed)
j 3.12 (Van Slyke)
I 3.29 (Olsen)

5.16

915

Examination of Milk Serum. — The most variable constitu-
ents of normal milk are the fat and protein, especially the former;
the least variable are the ash and milk sugar. The milk serum,
or milk from which the fat and protein have been removed, is,
therefore, of more unifonn composition than the milk itself,
hence better suited for the detection of adulteration and espe-

* /. Am. Chem. Soc, igoS, 1182.
t /. Ind. Eng. Chem., iQog, 253.

150 AIR, WATER, AND FOOD

cially of added water. The serum may be prepared by adding
to the milk some suitable precipitant of the protein, as calcium
chloride, acetic acid or copper sulphate. The clear liquid after
filtration may be examined for its content of dissolved solids,
its specific gravity or most conveniently by the immersion
refractometer.

The Copper Sulphate Method. '^ — Dissolve 72.5 grams of
crystallized copper sulphate in water and dilute to a liter. This
solution should be adjusted, if necessary, so that it will refract at
36 degrees on the scale of the immersion refractometer at 20° C.
or have a specific gravity of 1.0443 ^^ 20° C. compared with
water at 4° C. To one volume of the copper solution add
four volumes of milk, shake well and filter. The filtrate will
usually be clear after the first few drops have passed through.
On the clear filtrate either the refraction at 20° C, the specific

— ^ ) or the total solids may be determined.

Notes. — Examination of the copper serum from 150 samples of
known purity milk gave refractions varying from 36.1 to 39.5,
while the total solids of the same samples showed a range from
17.17 percent to 10.40 per cent and the fat varied from 7.7 per
cent to 2.45 per cent.

The minimum values for the copper serum of normal milk
are 36 degrees for the refraction at 20° C, 1.0245 for the specific

gravity \-^] and 5.28 per cent for total solids.

If the milk is already soured, it may be filtered and similar
determinations made on the natural sour serum, which for un-
watered milk should not refract below 38.3 or have a specific

gravity at 5-^ below 1.0229.

SPECIAL TESTS FOR ADULTERANTS

Cane Sugar. — Cane sugar may be present in milk from
diluted condensed milk used to eke out the supply or may be
present from calcium saccharate, added as a thickening agent.
* Lythgoe: Ann. Rpt. Mass. Bd. Health, 1908, 594.

ANALYTICAL METHODS 151

It is evident that any considerable amount which had been
added could be detected by the taste.

To detect the presence of cane sugar boil about 10 c.c. of the
milk with o.i gram of resorcin and i c.c. of strong hydrochloric
acid for five minutes. The liquid will be colored rose-red if
cane sugar is present. The color produced by heating should
not be confused with the pink color which may appear in the
cold if the milk contain certain coal-tar colors.

A similar test is the reduction of ammonium molybdate. As
recommended by Cotton * 10 c.c. of the milk are mixed with
0.5 gram of powdered ammonium molybdate and 10 c.c. of dilute
(i to 10) hydrochloric acid are added. In another tube 10 c.c.
of milk known to be free from sucrose are smiilarly treated and
the tubes placed in a water-bath, the temperature of which is
gradually raised to about 80° C. If sucrose is present, the
milk will gradually turn deep blue, while genuine milk remains
unchanged unless the temperature approaches the boiling point.
Cotton states that the reaction will detect as little as i gram
of cane sugar in a liter of milk.

Note. — Both of these tests, although used to detect cane
sugar, are in reahty tests for levulose, formed in this case by
the partial inversion of the sucrose.

Preservatives. — The preservatives most commonly employed
in milk are formaldehyde, boric acid or borax, and mixtures of
the two, and possibly hydrogen peroxide and fluorides. Sali-
cylic acid and sodium benzoate, although largely used in some
other classes of food materials, have been reported very rarely
as present in milk.

Formaldehyde. — This is the ideal preservative for milk,
being readily used and by far the most efficient. Quantities
which give a proportion in the milk of from i in 10,000 parts
to I in 50,000 are ordinarily employed. Such an amount will
suffice to preserve the milk for from 24 hours to several days.
Larger quantities, such as i part in 3000, will preserve the milk
for months. These large amounts, however, would be more or

* /. Pharm. Cliim., iSgj, 362.

152 AIR, WATER, AND FOOD

less apparent by the taste or odor. A tabular statement show-
ing the efficiency of formaldehyde in preserving milk as com-
pared with boric acid, borax and sodium carbonate will be found
in Leach's Food Analysis.

Several of the best tests for detecting formaldehyde are de-
scribed below. These may be applied directly to lo c.c. of the
milk, or as suggested in the gallic acid test, a larger quantity,
25 to 100 c.c, may be distilled and the test applied to the first
portion of the distillate.

(i) When the sulphuric acid is added to the milk in making
the Babcock test for fat, a bluish-violet ring will be noticed
at the junction of the two liquids when formaldehyde is present.
One part of formaldehyde in 200,000 parts of milk can be de-
tected by this test, but it fails when the formaldehyde amounts
to 0.5 per cent. The test is more delicate if the sulphuric acid
contains a trace of ferric chloride.

(2) To 10 c.c. of milk in a small porcelain dish add an equal
volume of hydrochloric acid (1.20 sp. gr.). Add one drop of
ferric chloride solution and heat the dish with a small flame,
stirring vigorously, until the contents are nearly boiling.
Remove the flame and continue the stirring for two or three min-
utes, then add about 50 c.c. of water. The presence of formal-
dehyde will be shown by a violet color which appears in the
particles of the precipitated casein, the depth of color depending
on the amount of formaldehyde present. The color should
be observed carefully at the moment of dilution. This test
readily shows the presence of one part of formaldehyde in
250,000 parts of milk, if fresh.

(3) Gallic Acid Test* — This test has been found by Shermanf
to be much more delicate than either of the preceding tests.
25 to 50 c.c. of the milk should be acidulated with phosphoric
acid and distilled. To the first 5 c.c. of the distillate add 0.2
to 0.3 c.c. of a saturated solution of gallic acid in pure ethyl

* Barbier and Jandrier: Ann. Chint. anal., i, 325; Mulliken and Scudder: Am.
Chetn. J., igoo, 444.

t /. Am. Chem. Soc, 1905, 1499-

ANALYTICAL METHODS 1 53

alcohol and pour it cautiously down the side of an inclined test
tube containing 3-5 c.c. of pure concentrated sulphuric acid.
If fonnaldehvdc is present a green zone is formed at the junction
of the two layers, gradually changing to a pure blue ring.

The delicacy of the test is about one part of formaldehyde in
500,000 parts of milk.

Notes. — It should be borne in mind that when small amounts
of formaldehyde are added to milk the ordinary tests will show
the presence of the preservative for only a short time. For
example, it has been shown by Williams and Sherman * that
when formaldehyde was added to milk in the proportion of i part
to 100,000 only a faint test was given after 48 hours standing;
and that the preservative had entirely disappeared in from three
to five days. This is due to the gradual formation of conden-
sation products of the formaldehyde with the proteins of the milk
which do not respond to the usual reaction. In such a case, it is
better to distill the milk as directed and apply the test with
gallic acid to the distillate. The test is thus made more delicate,
so that the preservative may still be shown when the simpler
tests have failed.

Another possible contingency is that some substance may be
added with the formaldehyde which will interfere with the tests
for its detection. Both hydrogen peroxide and nitrites prevent
the reaction of formaldehyde in the usual tests and preserva-
tives are on the market which are mixtures of fonnaldchyde
with hydrogen peroxide or a nitrite. The sulphuric acid test
and the hydrochloric acid-ferric chloride test can be used to
show the formaldehyde in the presence of considerably larger
quantities of nitrites by first removing the latter. Add to 10 c.c.
of the milk i c.c. of a 10 per cent solution of urea, then 2 c.c.
of dilute (i :4o) sulphuric acid and immerse the test tube in boil-
ing water for two minutes. Cool and carry out the test as usual.
The reaction between the urea and the nitrous acid may be
expressed :

CO (NHo)2 + 2 HXO, = COo + 2 No -t- 3 H.O.

* /. Am. Clicm. Soc, 190 j, 1497.

154 AIR, WATER, AND FOOD

Boric Acid or Borax. — Make 25 c.c. of the milk distinctly
alkaline with lime water and evaporate to dryness on the water-
bath. Char the residue over a flame but do not necessarily
heat it until white. Digest the residue with 15-20 c.c. of water
and add hydrochloric acid (1.12) until the mixture is faintly
acid to litmus paper. Filter, and add i c.c. of acid in excess.
Place a strip of turmeric paper in the solution and evaporate to
dryness on the water-bath. If boric acid or borates are present,
the paper takes on a peculiar red color, which is changed by
ammonia to a dark blue-green, but is restored by acid. Excess
of hydrochloric acid should be avoided, as it turns the paper a
dirty green when evaporated. This test can also be applied
to the hydrochloric acid solution of the ash.

Sodium Carbonate. — Detected in the milk-ash, as on page
141. If effervescence occurs, test the original milk with rosolic
acid as follows: Mix 10 c.c. of milk with an equal volume of
alcohol, and add a few drops of a one per cent solution of rosolic
acid. The presence of sodium carbonate is indicated by a more
or less distinct pink coloration. A comparative test should be
made at the same time with milk known to be pure.

Salicylic and benzoic acids. — If it is desired to test for these,
the following method may be employed. To 25 c.c. of milk add
100 c.c. of water and precipitate the proteins and fat with copper
sulphate and sodium hydroxide, as described on page 145.
Filter and add to the filtrate 5 c.c. of concentrated hydro-
chloric acid. Extract with ether and proceed as outlined on
page 196.

Coloring Matter. — The object in adding coloring matter to
milk is in general to disguise the bluish appearance of skimmed
or watered milk. For this reason it is rather unusual to find
added color in the case of milk which is of standard quality,
although such cases have been reported.

Formerly the chief color used was annatto, a reddish-yellow
coloring matter obtained from the seeds of Bixa Orellana, a
shrub growing in South America and the West Indies. A solution
of the color in very dilute alkali is employed. More recently

ANALYTICAL METHODS 1 55

various coal-tar dyes and even caramel have been used. The
latter is, perhaps, not so likely to be found, because its color
is too brown and not enough yellow to give the desired creamy
appearance to the milk which is so easily obtained with annatto.
The coal-tar colors, especially mixtures of yellow and orange
azo dyes, give very good results.

Leach * has suggested a general scheme for the identification
of these colors in milk, which with some modifications which
experience in the writer's laboratory has shown to be helpful
in detecting annatto especially, is given below.

Procedure. — Place about 100 c.c. of the milk in a small
beaker, add 3-4 c.c. of 25 per cent acetic acid (sp. gr. = 1.04),
stir thoroughly and allow the beaker to stand quietly on the
water-bath for about ten minutes, the casein being thus sepa-
rated as a compact cake. Decant off the whey, squeezing the
curd as dry as possible with a spatula. Transfer the curd to
a flask, cover it with ether, stopper tightly, and shake the flask
violently in order to break up the curd as much as possible.
Let it stand for several hours, preferably over night.

Pour off the ether, which contains the annatto, and evap-
orate {away from a flame) until no odor of ether remains. Add
5 c.c. of water and then dilute sodium hydroxide until the mix-
ture, after thorough stirring with a glass rod, is faintly alkaline
to litmus paper, and filter through a wet filter. If annatto is
present it will permeate the filter and give it an orange-brown
color which may readily be seen if the filter is removed from the
funnel and the fat washed off under the tap. Its presence may
be confirmed by touching the colored portion of the paper with
a drop of stannous chloride, which gives a pink color with annatto.

After pouring off the ether examine the milk-curd for caramel
or coal-tar color. If the curd is left white, neither of these
colors is present. If caramel has been used, the curd will be of
a pinkish-brown color; if the color is due to the coal-tar dye,
the curd will have a yellow or orange tint. If now some con-
centrated hydrochloric acid is poured over the curd, the color
* J. Am. Cfiem. Soc, igoo, 207.

156 AIR, WATER, AND FOOD

will change immediately to a bright pink with the coal-tar colors
ordinarily used.

Notes. — When the milk is curdled by the acid, any added color
is carried down by the curd. When this is subsequently treated
with ether the fat and annatto are dissolved, leaving any cara-
mel or coal-tar color still in the curd. Since the detection
of the two latter colors may depend upon recognizing color in
the curd, this should always be compared with the curd prepared
in the same manner from a sample of milk known to be free from
color.

The ordinary tests for caramel as used to show its presence
in distilled liquors or vanilla extract are not sufficiently delicate
to detect the extremely small quantity which suffices to impart
the desired shade of color to the milk. The color imparted to
the curd, however, is characteristic and readily recognized.

It is possible that coal-tar dyes may be used which do not
give the pink reaction with hydrochloric acid, since this is char-
acteristic in general only of the azo class of dyes. Even in
these cases, however, the orange color of the dye is readily per-
ceptible in the separated curd.

Milk colored with an azo dye may occasionally fail to show
its presence if the sample is old or partly decomposed before
being tested. This has been shown by Blyth * to be due to the
reduction of the dye by nascent hydrogen produced by the growth
of certain anaerobic organisms.

Interpretation of Results. — Apart from the addition of
foreign ingredients, such as colors and preservatives, which are
detected by the specific tests described, the most common forms
of adulteration are the addition of water and the removal of
cream. By reference to the table on page 136, it will be seen
that on account of the variation in the composition of unadul-
terated cow's milk the detection in all cases is not an easy prob-
lem. The variation in the fat content, especially, makes it
more difficult to show with certainty the partial removal of
cream than the addition of water.

* Analyst, 1902, 146.

ANALYTICAL METHODS

157

This is well shown in the following table in which "^ " is
a normal milk, "5" the same milk in which the fat has been
reduced to 3.6 per cent by adding water and "C" the same milk
in which the fat has been reduced to 3.6 per cent by skimming.

Total solids

12.78
4.00
2.89
5.00
0.71
8.78

11-34
3.60
2.60

4 50
0.64

7-74

12.09
3 60

Fat

Protein

2.91
4.98
0.72
8.6i

Sugar

Ash

Solids not fat

It is seen that in sample C it is only the fat that has been
decreased to any degree. In fact there is nothing in the figures
given for C to indicate in any way that the sample is not genuine
milk, while in B the soHds not fat are so low as to show the adul-
teration quite plainly.

Composition of Milk of Known Purity. — The average com-
position of milk, together with the usual and the extreme limits
of variation, have already been stated on page 136. The greater
number of published analyses of genuine cows' milk have been
limited to determination of sohds, fat and specific gravity. A
more detailed study, including the constants of the copper
serum, will be found in the following table,* which includes the
analyses of 33 samples of known purity milk from individual
cows, and 4 samples of herd milk, arranged in the order of their
percentage of total solids.

In collecting the samples milk was taken from the heaviest
milkers, so as to include a larger proportion of low-grade milk
for minimum values. None of the milk could be called excbp-
tionally high grade, as samples were not collected from Jersey or
Guernsey cows.

Inspection of this table shows, as would be expected, a great
variation in the percentage of fat in the individual samples, the
highest being almost 100 per cent higher than the minimum
values. The solids not fat are seen to present a much less

* Lythgoe: Bull. Mass. Bd. Health, 1910, 422.

158 AIR, WATER, AND FOOD

variation, and as Lythgoe has pointed out, this variation
is due very largely to the changes in protein content, the milk
sugar and ash remaining fairly constant. Upon this fact
depends the special value of an examination of the milk
serum.

In some cases all that may be necessary is to show by the
analysis that the milk does not conform to the legal standard.
In certain of the states, however, a legal distinction is made
between milk which is simply below standard and milk which has
been actually adulterated by skimming or watering. It is there-
fore of importance to show by the analysis whether water has
been added to the milk directly and not through the breed or
feed of the cow.

Detection of Watered Milk. — Since in general the water that
has been added is no different from the water already present
in the milk it is evident that this form of adulteration can be
detected only by showing chemical or physical changes in the
milk that could be ascribed only to the addition of water. Meth-
ods have been proposed, it is true, based on differences in the
added water, such as an abnormally high amount of nitrates,
which might have been derived from the polluted barnyard
well, but these methods are of little importance.

(a) Solids Not Fat. — Since the variation in proportion of
solids not fat in normal milk is much less than the range of
total solids this is of distinct value in showing added water.
Although as indicated in the table of limiting values on page 136,
the value for solids not fat may go as low as 7.5 per cent, this
is rather uncommon, and a fairer minimum would be 7.7 per
cent. A value below 7.7 per cent would certainly be suspicious
of added water and if accompanied by correspondingly low values
for the constants of the serum could be regarded as direct evidence
of adulteration.

(b) Milk Sugar. — As suggested by Lythgoe,* the milk sugar
may be employed to even greater advantage than the soHds not
fat in showing adulteration. Knowing the percentage of solids

* Loc. cit.

ANALYTICAL METHODS

159

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AIR, WATER, AND FOOD

and of fat, the protein may be calculated by the formulae given
on page 149. Then if 0.7 be assumed as the value for the ash,
the milk sugar may be determined by subtracting from the
total solids the sum of the other constituents. The expression
for the milk sugar would then become

(i) Milk sugar = T.S. - {F -\- [0.4 (7^ - 3) + 2.8] + 0.7).

T.S.

(2) Milk sugar = T.S. - (F +

T.S.

1-34.

+ 0.7).

The portion of the formula enclosed in brackets is the calcu-
lated protein in each case. In the case of pure milk the formulas
for calculating the protein will give very similar results, but
with adulterated milk they will be divergent, the difference,
increasing with the extent of adulteration. In the case of
watered milk the calculated milk sugar will be too low, ordinarily
falhng below 4.2 per cent, while, as will be shown later, with
skimmed milk, the milk sugar will be too high, generally above 4.8
per cent.

(c) Milk Serum. — If the preliminary calculation indicates a
possibility of the samples being watered an examination of the
serum should be made. This may be done preferably by the
copper sulphate method, which is described and the minimum
values for pure milk stated on page 150. The following table
due to Lythgoe shows the effect of systematic watering on the
composition of the milk and the constants of the serum in the
case of a milk which was above the average in solids not fat
and refraction.

COMPOSITION OF A SAMPLE OF MILK SYSTEMATICALLY
WATERED

Added

Solids

(per

cent).

Fat (per
cent).

Solids not
fat (per
cent).

Copper serum.

water

(per

cent).

Refrac-
tion, 20°.

specific

gravity,

20°

4°

Solids

(per

cent).

0
10
20
30
40
50

13.18

11.86

10 -54

9 23

7.91

6.59

4. 20
3.78
3.36
2.94
2.52
2. 10

8.98
8.08
7.18
6. 29
5-39
4-49

38.5
36.4
34-4
32.4
30.6
28.6

I .0272
I .0249
1.0233
I .0211
I .0194
I. 0174

6.09
5-57
5-05
4.56
4. 10
3-54

ANALYTICAL METHODS l6l

It is seen that each 5 per cent of added water lowers the
refraction by one scale division, hence with average milk,
refracting below 38 degrees, 10 per cent of added water could
be detected, and with rich milk 15 per cent can usually be
found.

Detection of Skimmed Milk. — Watering milk does not in
general change the relation of the various constituents to one
another, since these are all reduced in the same proportion,
but removing the fat does change these ratios. It is immaterial
whether the milk is skimmed by the actual removal of some of
the fat or whether separator skim milk is added to normal milk.
In either case the resulting product will have its fat content
largely reduced, while the proteins and sugar suffer but little
change. In normal milk, especially in the mixed milk of a herd,
the percentage of fat is rarely less than the protein (see table,
page 159). In 5500 analyses of American milks compiled by
Van Slyke, with a fat content between 3 and 5 per cent, the
average amount of fat was 3.92 per cent and the average amount
of proteins 3.20 per cent. If such milk be skimmed the fat may
be reduced to i per cent or even to o.i per cent but the protein
content will still be approximately the same as before. In the
calculation of milk sugar by the formulae given on page 160,
the same effect will be noticed, that is, the skimming will
lower the fat or the soHds to a greater extent than the protein.
Hence the proteins calculated from the fat or total solids will
be too low and the calculated milk sugar will be too high. For
practical purposes the limit for unskimmed milk may be set
at 4.8 per cent, values above this being suspicious of skimmed
milk.

In addition to this preliminary test, the milk may be with
certainty declared skimmed if the fat falls below 2.2 per cent,
the solids not fat remaining above the average value of 8.5
per cent. If the fat is above 2.2 per cent and below 3.5 per
cent, the presence of skimmed milk may be confirmed by making
a KJeldahl nitrogen detennination on the suspected sample and
calculating the proteins by the factor 6.38. If the proteins

l62 AIR, WATER, AND FOOD

exceed the fat, as stated in the preceding paragraph, the sample
is skimmed. If, however, the fat is above 3.5 per cent, this pro-
cedure will no longer suffice, since the proteins rarely exceed
3.5 per cent. In these few cases, the skimming can be judged
only from the high specific gravity, high solids not fat and cor-
respondingly low fat.

Specific Gravity of Milk Solids. — The specific gravity of the
milk solids is sometinies used to show skimming. Fleisch-
mann's formula for calculating this is

T.S.
^ o _ (100 X Gr) — 100
Gr

when T.S. = the total solids and Gr the specific gravity of the
milk.

Example. — A sample of milk contains 12.85 P^^ cent of milk
solids and has a specific gravity of 1.031. Required the specific
gravity of the milk solids.

i2.8t; i2.8t; ,

X ^ = = I.'^OO.

12 SS ^^^° ^ ^'^^^^ ~ ^°^ 12.85-3.006

1-031

The specific gravity of the solids of normal milk varies be-
tween 1.25 and 1.34. It is not changed by watering the milk,
but is increased by removing the fat or adding skimmed milk.
A value above 1.32 is suspicious while a specific gravity of the
milk solids above 1.40 is regarded as conclusive evidence of
skimming.

BUTTER

General Statements. — Butter consists of the fat of milk,
together with a small percentage of water, salt, and curd. The
curd is made up principally of the casein of the milk. These
various ingredients are present in about the following propor-
tions :

Fat 78.00-90.0 per cent; average, 82 per cent.

Water 5.00-20.0 per cent; average, 12 per cent.

Salt 0.40-15.0 per cent; average, 5 per cent.

Curd o.ii- 5.3 per cent; average, i per cent.

ANALYTICAL METHODS

163

The fat consists of a mixture of the glycericles of the fatty
acids. The characteristic feature of butter-fat is the extraor-
dinarily high proportion of the glycerides of the soluble and
volatile fatty acids when contrasted with other fats.

The following may be taken as the probable composition
of normal butter-fat : *

Acid.

Per cent
Acid.

Per cent
Triglycerides.

Dioxystearic

I .00
32.50

1.83
38.61

9.89

2.57
0.32
0.49
2.09
5.45

1 .04

33.95
1. 91

40.51
10.44

2.73
0.34
0.53
2.32
6.23

Oleic

Stearic

Palmitic

Myristic

Laurie

Capric

Caprylic

Caproic

Butyric

Total

94-75

100.00

According to this, the proportion of volatile acids in butter
(butyric, caproic, caprylic and capric acids) amounts to 8.35 per
cent. The amount of volatile acid in lard, for example, is about
0.1 percent.

The usual examination of butter consists in the examina-
tion of the butter-fat, in order to detect the presence of foreign
fats. Those commonly used for this purpose are lard, oleo-
margarine, and sometimes butter substitutes containing cocoanut
oil.

The term "oleomargarine" is usually applied to a mixture
of refined lard, "oleo oil," which is mainly the olein of beef fat,
and cottonseed oil. Ordinarily a small proportion of butter
is added and the product is generally churned with milk.

A comparatively recent form of butter substitute which
finds extensive use in some sections of the country is " process,"
or "renovated," butter. The raw material, or "stock," used for
the manufacture of this consists of butter which cannot be sold

* Browne: /. Am. Chem. Soc, iSgg, 807.

164 AIR, WATER, AND FOOD

as butter either because of deterioration through rancidity or
molding or because, through carelessness on the part of the
makers, it possesses an unattractive appearance or flavor. The
chief recruiting-ground for this material is the country grocery
store. The fat, separated from the curd by melting and settling,
is aerated to remove disagreeable odors and leave it nearly
neutral. This is then emulsilied with fresh milk which has
been inoculated with a bacterial culture, and the whole is chilled,
granulated, and churned. The butter is then worked and packed
for market in the usual manner. The character of the product
has much im.proved since the early days of the industry, the
best grades now approximating the lower grades of creamery
butter.

The "aroma" of butter seems to be connected with the decom-
position produced by the action of bacteria on the casein and
the small amount of milk-sugar that is present, and not with
any change in the fats; there is no evidence, however, that any
unwholesome effect is produced by the aroma-giving organisms.

The rancidity of butter-fat is generally considered to be
due to decomposition and oxidation of the fatty acids, espe-
cially the unsaturated ones, the amount of change depending
on conditions of light, heat, and exposure to air.

Analysis of Butter. — Apart from the examination of the
butter fat to detect the addition of foreign fats, butter itself
is often analyzed in order to determine variations in its con-
stituents from the normal, or the addition of deleterious
substances.

The Federal standard for butter describes it as "the clean,
non-rancid product made by gathering in any manner the fat
of fresh or ripened milk or cream into a mass, which also con-
tains a small portion of the other milk constituents, with or
without salt, and contains not less than eighty-two and five-
tenths (82.5) per cent of milk fat. By acts of Congress approved
August 2, 1886, and May 9, 1902, butter may also contain added
coloring matter."

The determinations usually made to ascertain whether the

ANALYTICAL METHODS 1 65

butter is of standard quality arc the water, fat, ash, curd, and
salt. Of these the first four can be made on the same weighed
sample, following in general the methods recommended by the
Association of Official Agricultural Chemists.*

The following method is simpler and gives results comparable
with the official methods:

Weigh about 2 grams of butter into a platinum Gooch cruci-
ble, half-iilled with ignited fibrous asbestos, and dry it at 100° C.
to constant weight. The loss in weight is the amount of water.
Then treat the crucible repeatedly with small portions of pe-
troleum ether, using gentle suction, and again dry it to constant
weight. The difference between this and the preceding weight
will be the amount of fat. Now carefully heat the crucible
over a small flame or in a muffle until a light grayish ash is
obtained. The loss in weight is the amount of curd, and the
residual increase in weight over that of the crucible and asbestos
is the ash. If desired, the salt may be washed out of the ash
and determined by titration with silver nitrate after neutraliz-
ing the solution with calcium carbonate.

Notes. — If the sample for analysis is to be taken from a
considerable quantity of butter, great care must be taken in
sampling, because the butter is usually not homogeneous in
composition and cannot be mixed by stirring. The best plan
is to take a fairly large sample of 100 to 200 grams or more,
melt it at the lowest possible temperature in a jar or wide-
mouthed glass-stoppered bottle and mix by \dolent shaking.
Then cool until sufficiently solid to prevent the separation of the
fat and water, taking especial care to shake the sample thor-
oughly during the cooling.

Rapid methods for the determination of water in butter have
been devised by Patrick f and Gray | especially for the exami-
nation of large numbers of samples.

Good butter should in general contain not less than the amount

* Bur. ofCliem., Bull. 107 {Rev.), p. 123.
t /. .\»i. Cliem. Soc, 1007, 1126.
t Bur. .\nimal Ind., Circ. icx3.

1 66 AIR, WATER, AND FOOD

oi fat required by standard, not more than 2.0 per cent of curd,
and not over 16 per cent of water.

5a//. — If a direct detennination of salt is desired, the fol-
lowing method, although tedious, will give satisfactory results:

Weigh 10 grams of butter in a small beaker, add 30 c.c. of

hot water, and when the fat is completely melted transfer the

whole to a separatory funnel. Shake the mixture thoroughly,

allow the fat to rise to the top, and draw off the water, taking

care that none of the fat-globules pass the stopcock. Repeat

the operation four times, using 30 c.c. of water each time. Make

the washings up to 250 c.c, mix thoroughly, and titrate 25

. . . N .

c.c. in a six-inch porcelam dish, usmg — silver nitrate with

potassium chromate as an indicator.

Preservatives. — About 50 grams of butter are mixed with
25 c.c. of chloroform in a separatory funnel, 100 c.c. of dilute
(o.i per cent) sodium carbonate solution added, and the whole
mixed, avoiding violent shaking. After the separation of the
layers, which may be greatly aided by a suitable centrifuge,
the aqueous layer is examined for preservatives, especially for
boric, benzoic and salicylic acids, by the methods described on
pages 154 and 196.

Colors. — No methods are described for the detection of
colors in butter since these, being allowed, do not constitute
an adulteration. If it be desired to test for added color in oleo-
margarine, methods may be found in Allen's Commercial Organic
Analysis, 4th Ed., Vol. II, or in Leach's Food Analysis.

Examination of the Fat. — The fat is first separated from the
other constituents of the butter so that it may be weighed out
for the various tests.

Directions. — Melt a piece of butter, about two cubic inches,
in a small beaker placed on top of the water-bath so that the
temperature shall not rise above 50° to 60°. After about fifteen
minutes the water, salt, and curd will have settled to the bottom.
(A better separation may be secured by dividing the melted
sample equally between two test-tubes and whirling them for

ANALYTICAL METHODS 167

3 to 4 minutes in a centrifugal machine.) Place a bit of absorb-
ent cotton in a funnel, previously warmed, and decant off the
clear fat through the cotton into a second beaker, taking care
that none of the water or curd is brought upon the filter. When
the filtered fat has cooled to about 40° place a small pipette in
the beaker and weigh the whole.

By means of the pipette the desired amount of fat is taken
out, the pipette replaced in the beaker, and the whole again
weighed. The difference in weight gives the exact amount
of fat taken. It is a saving of time, however, if several por-
tions are to be weighed out, to make the weights one after
another, so that one weight will suffice for a determination.
Weigh out thus: Two portions of 5 grams each into 250-c.c.
round-bottomed flasks for the Reichert-Meissl method, one
portion of 2.5 to 3 grams into a 500-c.c. beaker for Hehner's
process, two portions of about 0.35 to 0.5 gram each into 300-c.c.
glass-stoppered bottles for determination of the iodine value.
In the case of the larger portions, weigh only to the nearest
milligram.

(i) Reichert-Meissl Number for Volatile Fatty Acids — Di-
rections. — To the fat in the 250-c.c. flasks add 2 c.c. of strong
caustic potash (i : i) and 10 c.c. of 95 per cent alcohol. Connect
the flask with a return-flow condenser and heat on a water-
bath so that the alcohol boils vigorously for 25 minutes. At
the end of this time, disconnect the flask and evaporate off the
alcohol on a boiling water-bath. After the complete removal of
the alcohol, add 140 c.c. of recently boiled distilled water which
has been cooled to about 50 degrees. The water should be added
slowly, a few cubic centimeters at a time. W'arm the flask on
the water-bath until a clear solution of the soap is obtained.
Cool the solution to about 60 degrees and add 8 c.c. of sulphuric
acid (i : 4) to set free the fatty acids. Drop two bits of pumice,
about the size of a pea, into the flask, close it by a well-fitting
cork, which is tied in with twine, and immerse it in boiling
water until the fatty acids have melted to an oily layer floating on
the top of the liquid. Cool the flask to about 60 degrees, re-

l68 AIR, WATER, AND FOOD

move the cork, and immediately attach the flask to the
condenser.

Distill no c.c. into a graduated flask in as nearly thirty min-
utes as possible. Thoroughly mix the distillate, pour the whole
of it through a dry filter, and titrate loo c.c. of the mixed filtrate

N . . ...

with — sodium hydroxide, using phenolphthalem as an mdicator.

Multiply the number of cubic centimeters of alkali used by

eleven-tenths, and correct the reading also for any weight of

fat greater or less than 5 grams.

For example, if 5.3 grams of butter-fat are used, and 100 c.c.

N
of the distillate require 27.4 c.c. of — NaOH, no c.c. would re-

quire 27.4 X y^ = 30.14 c.c. Then 5.3 : 30.14 = $ : x. x =

28.4. X is the Reichert-Meissl number.

Notes. — The Reichert-Meissl number for genuine butter
varies from 24 to 34; the average usually taken is 28.8.

Cocoanut oil gives a value of 6-8; other edible fats and oils
have a value usually less than i .

Cocoanut oil is used, to some extent, as a substitute for butter
in confections and crackers, in cooking fats, and also in cocoa-
butter substitutes. Its presence is indicated by the Reichert-
Meissl number taken in connection with the saponification value,
that is, the number of milligrams of potassium hydroxide re-
quired to saponify one gram of the fat. (For a description of
the method of determining this see Lewkowitsch: Oils, Fats
and Waxes; or Gill: A Short Handbook of Oil Analysis.) The
Reichert-Meissl number is higher in butter fat than in cocoanut
oil, while the saponification value is lower. In pure butter fat
the value of the expression:

Saponification value — (Reichert-Meissl number — 200) varies
from 3.4 to 4.1; in pure cocoanut oil, it runs from 47 to 50.7.*

Another method of value in showing the presence of cocoanut
oil is the determination of the Polenske numberf which repre-

* Juckenack and Pastcrnack: Ztschr. Nahr. Gemissm., 7, 1904, 193.
t Polenske: Zlschr, Nahr. Gcnussm., 1904, 273.

ANALYTICAL METHODS 1 69

sents the volatile fatty acids insoluble in water. This value for
butter is from i to 3; for cocoanut oil, from 16 to 18. Details
of the procedure, which it requires some experience to carry out
successfully, may be found in the original paper or in Leach's
Food Analysis, 3d ed., page 483.

The reactions involved in the Reichert-Meissl method may be
simply explained as follows:

When the fat is treated with potash it is decomposed, the
glycerine being set free, and the potassium salts of the fatty
acids, that is to say, the potassium soaps, are formed. Hence
the process is called saponification. For butyric acid the re-
action may be expressed,

C3H5(C3H7COO)3 + 3 KOH = 3 C3H7COOK + C3H5(OH)3.

The alcohol is used to dissolve the fat. But at the moment
the butyric acid is set free it tends to combine with the alcohol to
form a volatile ether:

C3H7COOH + C2H5OH = C3H7COOC0H5 + HoO.

The object of the return-flow condenser is to prevent the escape
of this volatile ether and to allow of its complete saponification.

If the water used to dissolve the soap is added too rapidly,
the soap may be decomposed with the liberation of the fatty
acids: C3H7COOK + H.2O = C3H7COOH + KOH.

The fatty acids are set free at the proper time by means of
sulphuric acid, and the volatile acids distilled off and titrated.
The pumice is added to prevent explosive boiUng.

The whole of the volatile acids do not pass over into the dis-
tillate, but only a part, the amount depending upon the rate of
distillation and the volume of the distillate. Hence, in order to
get uniform results, it is necessary to follow the prescribed pro-
cedure with great care.

In Great Britain all determinations of the Reichert-lNIeissI
number, which are likely to lead to prosecutions under the ]\Iar-
garine Act, must be made in a specified apparatus, the dmiensions
of which are definitely stated and the procedure exactly defined.*

* Analyst, 25, 1900, 309.

lyo AIR, WATER, AND FOOD

Some of the errors in the Reichert-Meissl method may be
avoided, and the process materially shortened by carrying out
the saponification with glycerol and caustic soda as recommended
by Leffman and Beam.* The method is as follows:

Weigh 5 grams of the fat into a 250-c.c. round-bottomed
flask and add 20 c.c. of glycerol-soda solution. f Hold the flask
with tongs, and heat it directly over a flame until foaming ceases
and the mixture becomes perfectly clear, which ordinarily re-
quires about five minutes. Add to the clear soap solution 135
c.c. of water, adding it at first in very small portions to prevent
foaming. Finally add the pumice and sulphuric acid, as in the
Reichert-Meissl method, and distill without previous melting of
the fatty acids.

(2) Hehner's Method for Direct Determination of the Fixed
Fatty Acids. — Directions. — To the portion of 2.5 grams
weighed out into the 500-c.c. beaker add i c.c. of caustic potash
and 20 c.c. of 95 per cent alcohol. Cover the beaker with a
watch-glass and heat it on the water-bath until the liquid is
clear and homogeneous. As it is not essential to prevent the
escape of the volatile acids, the use of a return-flow condenser
is not necessary. Evaporate off the alcohol on the water-bath
and dissolve the soap in about 400 c.c. of warm distilled water.
When the soap is completely dissolved, add 10 c.c. of hydro-
chloric acid (sp. gr. 1.12), and heat the beaker in the water-
bath almost to boiling until the clear oil floats. Meanwhile, dry
and weigh a thick filter in a small covered beaker. Allow the
solution to cool until the fat forms a sohd cake on top; filter the
clear liquid and finally bring the solid fats upon the weighed
filter. Wash the beaker and fat thoroughly with cold water,
then wash out the fat adhering to the beaker with boiling water,
which is poured through the filter, taking care that the filter is
never more than two-thirds full. If the filter paper is of good
texture and thoroughly wet beforehand, it will retain the fatty
acids completely. If, however, oily particles are noticed in the

* Analyst, i8gi, 153.

t 20 c.c. of 50 per cent caustic soda solution to 180 c.c. of glycerol.

ANALYTICAL METHODS 171

filtrate, cool it by adding pieces of ice, remove the solidified par-
ticles with a glass rod and transfer them to the filter. Cool the
funnel by plunging it into cold water, remove the filter, place it
in the weighing-beaker, and dry it at 100° to constant weight.
The fat should be heated about an hour at first, then for periods
of about thirty minutes, until the weight is constant within
2 mgs.

Notes. — 87.5 per cent is usually taken as the proportion of
fixed fatty acids in butter-fat; 88 and 89 per cent have been
frequently found. All other fats yield from 95 to 96 per cent
of insoluble fatty acids.

(3) Determination of Iodine Value. — This method is based
on the fact that certain of the fatty acids, notably the "unsatu-
rated acids," as oleic acid, C17H33COOH, take up the halogens
with the formation of addition products.

Directions. — Dissolve the fat in the 300-c.c. bottles in 10 c.c.

of chloroform. Add 30 c.c. of the iodine solution from a pipette

or glass-stoppered burette, and allow the bottles to stand with

occasional shaking for thirty minutes. Add 10 c.c. of 20 per

cent potassium iodide solution and mix thoroughly, then 100 c.c.

. . . N
of distilled water, and titrate the excess of lodme with — sodium

thiosulphate until the solution is faintly yellow. Add 2 to 3 c.c.
of starch solution and titrate to the disappearance of the blue
color. Toward the end of the titration shake the bottle vigor-
ously so that any iodine remaining in the chloroform may react
with the thiosulphate. Calculate the result in grams of iodine
absorbed by 100 grams of fat. This is called the Iodine
Number, or Iodine Value.

At the time of making the determination carry out two
"blanks" in exactly the same way except that no fat is used.

Standardization of the Thiosulpliate Solution. — As this is not
pennanent, its strength should be determined by means of the
standard potassium bichromate solution, i c.c. of which is
equivalent to 0.0 1 gram of iodine.

Measure 20 c.c. of the potassium bichromate from a pipette

172 AIR, WATER, AND FOOD

into an Erlenmeyer flask. Add 5 c.c. of potassium iodide, 100
c.c. of water, and 5 c.c. of strong hydrochloric acid. Titrate the
liberated iodine with the thiosulphate solution until the color
has almost disappeared, then add starch solution and continue
the titration until the blue color disappears, leaving the sea-
green color of the chromium chloride. The iodine is Hberated in
accordance with the following equation:
KsCr.Oy + 14 HCl + 6 KI = 8 KCl + 2 CrCls + 7 H2O + 6 I.

Calculation of Results. — Example. — From the standardi-
zation,

16.07 c-c. thiosulphate = 20 c.c. bichromate = 0.200 gram I;
I c.c. thiosulphate = 0.0125 gram I.

Also, from blank,

30 c.c. iodine solution = 63.60 c.c. thiosulphate.

If 44.85 c.c. thiosulphate were used to titrate the excess of
free iodine, 63.60 — 44.85 = 18.75 c.c. is the amount of thio-
sulphate equivalent to the iodine combined with the fat. If
0.3271 gram of fat were used, since i c.c. thiosulphate is equiva-

1 . . r • J- 18.75 X 0.0125 ^^ , .

lent to 0.0121: gram free lodme, — — X 100 = 71.66

0.3271

grams of iodine combined with 100 grams fat.

Notes. — The Iodine Number of butter fat varies between 26
and 38; of oleomargarine, between 60 and 75; of lard, between
46 and 70; of cottonseed oil, from 106 to no; and of cocoanut
oil, between 8 and 9.5.

The products formed by the action of iodine on the fats are
mainly addition products with a slight proportion of substituted
bodies. Thus the unsaturated olein,

(CnH33COO)3C3H5,

takes up six atoms of iodine, forming an addition product,
di-iodo-stearin, (Ci7H33l2COO)3C3H5.

The method in general use for determining the iodine value
of fats and oils has been that of Baron Hiibl,* an alcoholic solu-

* Ding. Poly. J., 253, 281; /. Soc. Chem. Ind., 3, 1884, 641.

ANALYTICAL METHODS 1 73

tion of iodine and mercuric chloride being used as the reagent.
The method here described, due to Hanus,* has the advantage
that the solutions keep better, remaining practically unchanged
for several months, and that the action is about sixteen times
as rapid. For the fats and for oils with low iodine values, the
results are very close to the figures obtained by the Hiibl proc-
ess. If it is desired to carry out the determination by the
older method, directions can be found in any standard work on
the analysis of oils.

It should be noted that the "iodine solution" is a solution of
iodine bromide in glacial acetic acid, hence great care should be
taken that there is no change in temperature between the time
of measuring the solution of iodine for the blanks and for the de-
terminations, since the high coefficient of expansion of acetic
acid may cause a material error.

Further, the amount of fat taken for the analysis should be
such that only a portion of the iodine is absorbed, 60 to 70 per
cent being in excess. Care should also be taken to avoid vigor-
ous shaking of the glass-stoppered bottles until near the end of
the titration to prevent loss of iodine from the stopper.

(4) Refractive Index. — The determination of the refractive
index is especially valuable in the examination of butter, and for
that matter, in food analysis in general, owing to the rapidity
with which the test can be made and the fact that so Httle of the
substance is required. Various forms of refractometers are
used for the purpose, a fairly complete description of which
will be found in some of the larger works, such as Leach: Food
Inspection and Analysis; or Vaubel: Quantitative Bestimmung
organischer Verbindungen. The instrument having the widest
range is the Abbe refractometer, in which the index of re-
fraction is determined by measuring the total reflection pro-
duced by a very thin layer of the melted fat, placed between two
prisms of flint glass. This instrument, fltted with watcr-jackctcd
prisms, is shown in Fig. 13.

Directions. — Revolve the whole instrument on the axis h until
* Ztschr. Unlcrs. Nahr. it. Goiussm., 4, igoi, 913.

174

AIR, WATER, AND FOOD

it reaches the stop provided, then open the prism casing AB hy
giving the pin v a half-turn (to the right). Be sure that the
prism surfaces are clean. If not, clean them carefully with a soft
cloth and a little alcohol. Place a few drops of the melted

Fig.

13-

sample directly on the surface of the prism and clamp the two
together again by turning the pin v in the opposite direction.
Now turn the instrument back (toward the observer) as far as
possible and bring the "critical line" into the field of vision of
the telescope. This is done by holding the sector S firmly with
the hand and revolving the double prism by means of the alidade
/ until the field is divided into a light and a dark portion. If

ANALYTICAL METHODS

175

the line is not sharp focus the ocular of the telescope. If it is
colored it is due to dispersion of the light by the liquid and
should be corrected by revolving the compensator T by the
milled screw M. The correction is made by a system of two re-
volving Amici prisms in the lower part of the telescope. Adjust
the critical line so that it falls on the intersection of the cross
hairs of the telescope. Observe the temperature by the ther-
mometer inserted in
the prism casing. In
the case of solid fats,
a sufficiently high
temperature should
be maintained by a
current of warm
water to keep the
sample well above its
melting point. A
temperature of 30 to
40° C. is usually suffi-
cient. Do not let the temperature rise above 70° or the prisms
may be injured. Read the index of refraction directly through
the small lens L, estimating the fourth decimal. Calculate the
value for the refractive index at 25° C.

Notes. — The principle on which the Abbe refractometer is
based will, perhaps, be more clearly understood by reference to
Fig. 14.

Let AB ht the surface of separation between two media, of
which the upper is the rarer, and let a beam of light pass through
in the direction 10. It will be seen that as the light passes from
the denser to the rarer medium, the angle of refraction r will be
greater than the angle of incidence i. If the angle of incidence
be increased, then for a certain incident angle, the angle of re-
fraction will become 90°, that is, the refracted ray will coincide
with the dividing surface. For incident rays striking the sur-
face at a greater angle than this, the light will be totally reflected
and there will be no refracted ray. The angle of incidence at

Fig.

14.

176

AIR, WATER, AND FOOD

which this occurs is known as the critical angle.

. sin i

Then since n = —. — ,
stn r

... , sin i sin i . .

at the critical angle n = —. x = = sm i.

sm 90 I

That is, in passing from a denser to a rarer medium, the index of
refraction is equal to the sine of the angle of incidence for the
border line of total re-
flection. ' ^^ ^ ^

In the Abbe rcfrac-
tometer the refractive
index of the liquid is
determined by measur-
ing the critical angle
for light passing into
it from a glass prism of
higher refractive index. The sine of
this angle is the index of refraction
of the liquid, referred to glass, and
this multiplied by the refractive in-
dex of the glass gives the index of
refraction of the liquid referred to air.
The divisions on the scale are pro-
portional to the sines of the angles
of incidence for total reflection, multi-
plied by 1.75, the refractive index of
the prism and, therefore, give directly
the refractive index of the substance
examined. Since the light must pass
from the denser to the rarer medium,
it is evident that the instrument is
limited to liquids whose refractive indices are less than 1.75.

Fig. 15, from Browne's Handbook of Sugar Analysis, illus-
trates diagrammatically the passage of light through the in-
strument. The heavy line represents the border line of total
reflection, the light striking the surface AB at a. less angle being

Fig. 15.

ANALYTICAL METHODS

177

refracted, and illuminating the field of the telescope. The rays
which fall upon the surface at a greater angle are totally reflected,
leaving the corresponding portion of the telescopic field dark.

The index of refraction decreases with rising temperature.
With the common oils and fats, the change for each degree is
very nearly a constant, amounting to 0.000365. Leach and
Lythgoe * have devised a sliding scale by means of which the
temperature correction may be readily made without reference to
tables.

The values of «|^ for genuine butter lie between 1.4590 and
1.4620; for oleomargarine the values range from 1.4650 to
1.4700.

The correctness of the instrument should be tested by the
"test-plate" which comes with it, cementing it to the prism
with monobromnaphthalene, or the testing may be done more
conveniently with distilled water. The refractive index of wat6r
at ordinary temperatures is given below:

Tempera-

Refractive

Tempera-

Refractive

ture, °C.

Index.

ture, °C.

Index.

^■3332

13327

I-333I

1.3326

1-3330

1-3325

I 3329

1-3324

1.3328

1-3323

Special Tests for Distinguishing Renovated Butter. — Spoon
Test or "Foam'' Test. — Melt a piece of the sample as large as a
small chestnut in an ordinary tablespoon or a small tin dish.
Use a small flame and stir the melting fat with a splinter of wood
(such as a match). Then increase the heat so that the fat shall
boil briskly, and stir thoroug/dy, not neglecting the outer edges,
several times during the boiling.

Oleomargarine and renovated butter boil noisily, usually
sputtering like a mixture of grease and water when boiled, and

* J. Am. Chem. Soc, 1904, 1193.

178 AIR, WATER, AND FOOD

produce little or no foam. Genuine butter usually boils with
much less noise and produces an abundance of foam, often rising
over the sides of the dish or spoon when the latter is removed
temporarily from the flame. The difference in regard to the
foam is very marked.

Note also the appearance of the particles of curd after the
boiling. With genuine butter these will be very small and
finely divided, hardly noticeable in fact, while with oleomargarine
and renovated butter the curd gathers in much larger masses
or lumps.

Notes. — This simple method is of value for giving a quick
decision regarding a sample, and is especially useful for the
detection of renovated butter. The dififerences in the compo-
sition of butter-fat brought about by renovation are so slight
that chemical methods are here of no avail.

The spoon test, however, will distinguish in the great majority
of cases between genuine butter on the one hand and oleo-
margarine and renovated butter on the other; the index of
refraction or the chemical methods just described readily dis-
tinguish between the two latter.

In genuine butter the curd is somewhat different in compo-
sition from that of renovated butter or oleomargarine in that it
consists largely of the milk proteins that are insoluble in water,
and hence accompany the separated cream. The curd of reno-
vated butter or oleomargarine, on the other hand, comes from
the proteins of the milk added directly in the process of manu-
facture, and consists mainly of coagulated casein. Hence its
different appearance in the test.

The crackhng and sputtering of the fat in the case of oleo-
margarine and renovated butter are due to the fact that in the
process of manufacture of these the melted fat is sprayed into
ice-water, and the cooled particles enclose some water.

Microscopic Examination. — Pure, fresh butter is not ordi-
narily crystalHne in structure. Butter which has been melted,
however, and fats which have been liquefied and allowed to cool
slowly show a distinct crystalline structure, especially by polar-

ANALYTICAL METHODS 179

ized light. If only fresh butter were sold, and all adulterants
had been previously melted and slowly cooled, this method would
be all that would be necessary for the detection of adulteration.
As it is, however, it is most useful in making comparative exami-
nations of samples which have been subjected to the same
conditions.

About the most that can be said is that if a small bit, about
the size of a pin-head, of the fresh, unmelted sample, is taken
from the center of the mass and pressed out on a sUde by gentle
pressure on the cover glass, it ought to show a fairly uniform
field if examined with a one-sixth objective, using polarized
light and a selenite plate. Other fats melted and cooled, and
mixed with butter, generally show a crystalline structure and a
variegated color with the selenite plate.

In the case of renovated butter, however, there is a distinct
difference to be noted in the appearance of the field. With
genuine butter the field is much more clear and free from opaque
masses of curd than with renovated butter. When the slide is
examined by reflected light, turning the mirror so as not to pass
light through the slide, these opaque masses in the case of reno-
vated butter show strikingly as white masses against a dark
background.

CEREALS

The great importance of cereal food in the diet may be
gathered from the fact that dietary studies among a large num-
ber of American families have shown that about three-fourths
of the vegetable protein, one-half of the carbohydrates, and
seven-eighths of the vegetable fat are supplied by the cereals.
The reason for such an extensive use of the cereals lies in the
fact that, besides being cheap and easily grown, they contain
unusually large proportions of nutriment with a very small pro-
portion of refuse. They are readily prepared for the table, are
palatable and digestible. In distinction from the two classes of
food materials already considered, they are in a dry fomi, and
not liable to rapid change by micro-organisms.

l8o AIR, WATER, AND FOOD

Prepared breakfast foods may be taken as typical and inter-
esting cereal products, and since many of these are somewhat
modified from their original composition by cooking or by
treatment with malt, the form in which the carbohydrates are
present is of almost equal importance with the determination of
nitrogen.

The fact that in the breakfast cereals the process of manu-
facture has in no way increased their actual food value over the
grains from which they were prepared, as pointed out in Chapter
VIII, is emphasized by the figures in the accompanying table in
which some of the most widely-used preparations are compared
with the original grains. It will be observed that practically the
only change is in the solubility of the carbohydrates, the starch
being changed in part to dextrin. In the case of the malted food,
the change may go even farther, and a greater or less amount of
reducing sugar, principally maltose, be formed.

Moisture. — Directions. — Spread about 2 grams of the
finely ground material in a thin layer on a watch-glass and dry
it in the oven at 100° C. for five hours. On account of the
ready absorption of moisture by the dried sample, the use of
clipped watch-glasses will be found advantageous.

Note. — With some substances drying in a current of hydro-
gen or some inert gas may be necessary, but for most cereals the
method given will be found satisfactory.

Ash. — Directions. — Weigh about 2 grams into a platinum
dish, such as is used for the determination of solids in milk, and
char it carefully. Ignite at a very low red heat until the ash is
white, preferably in a mufSe.

Notes. — If a white ash cannot be obtained in this manner,
exhaust the charred mass with water, collect the insoluble
residue on a filter, burn it, add this ash to the residue from the
evaporation of the aqueous extract and heat the whole at a low
red heat until the ash is white.

Some cereals, such as whole wheat and barley, will act de-
structively on platinum dishes, on account of the phosphates
present, but can be ignited safely in platinum in the muffle.

ANALYTICAL METHODS

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l82 AIR, WATER, AND FOOD

Fat: Ether Extract. — Dircclions. — Place the residue from
the determination of moisture, as described above, in a porous
paper cup and extract it with pure anhydrous ether for sixteen
hours, using the Soxhlet extractor and electric heater as de-
scribed on page 141. Evaporate off the ether and dry the
residual fat at the temperature of boiling water to constant
weight.

Note. — The ether extract of cereals is not pure fat but may
contain more or less coloring matter or resins. Petroleum ether
can be used for the extraction, giving results not essentially
different from those obtained with anhydrous ethyl ether.

Total Protein: Determination of Nitrogen by the Kjeldahl
Process.* — This method is based upon the decomposition of
the nitrogenous material by boiling with strong sulphuric acid.
The carbon and hydrogen are oxidized to carbon dioxide and
water, a portion of the sulphuric acid being reduced to sulphur
dioxide. The nitrogen is left as ammonium sulphate from
which the ammonia is liberated by potash or soda and distilled
into a known excess of standard acid. The time of digestion
can be materially shortened by the use of substances like mer-
cury or potassium sulphate which assist the oxidation or raise
the boihng-point of the acid.

Directions. — Transfer about 0.5 gram of the finely divided
substance from a weighing-tube to a pear-shaped digestion flask,
add 10 c.c. of concentrated sulphuric acid free from nitrogen,
and 0.2 gram (three small drops) of metallic mercury. Place a
small funnel in the neck of the flask, which should be sup-
ported in an inclined position on wire gauze and heated with a
small flame until frothing has ceased and the liquid boils quietly.
Then increase the heat and boil the solution for at least an
hour after it becomes colorless. Allow the flask to cool for a
minute or two, and add a few crystals of potassium permanganate
until the liquid has acquired a slight green or purple color.

N
Measure 25 c.c. of — acid from a burette into a 300-c.c.

* Ztschr. anal. Client., 22, 1SS3. 366.

ANALYTICAL METHODS 183

Erlenmeyer flask and place the condenser-tip beneath the

surface of the liquid, adding a little water, if necessary, to seal

it.

Transfer the digestate with several small portions of distilled

water to the distilling flask of the apparatus, add 20 c.c. of

potassium sulphide solution, and connect the flask with the

condenser. Add 50 c.c. of caustic potash through the separa-

tory funnel, and distill off the ammonia by steam. When 200

c.c. have distilled over, remove the collecting-flask, after rinsing

off the condenser-tip with distilled water, and titrate the excess

N . . .

of acid with — sodium hydroxide, usmg methyl orange or
10

cochineal as indicator. If using new reagents, a blank deter-
mination should be made with 0.5 gram of cane-sugar in order
to reduce any nitrates present which might otherwise escape
detection.

Notes. — The temperature during the digestion must be
maintained at or near the boiling-point of the acid, since at a
lower temperature the formation of ammonia is incomplete.

In some cases, the potassium permanganate is necessary to
insure the complete conversion of the nitrogenous bodies into
ammonia, although it is probable that its use is unnecessary in
the majority of analyses.

The addition of potassium sulphide before distilling is to pre-
cipitate the mercury and thus prevent the formation of non-
volatile mercur-ammonium compounds.

The Kjeldahl process in the form outlined above is not ap-
plicable to the determination of nitrogen in the form of nitrates.
In order to render it of more general application various modi-
fications of the method have been proposed, the one generally
used in this country being that suggested by Scovcll.* In this
method salicylic acid is used with the sulphuric acid, being con-
verted by the nitrate into nitro-phenol. By the use of sodium
thiosulphate or zinc-dust this is reduced to amido-phenol. The
amido-phenol is transformed into ammonium sulphate by the
* U. S. Dept. Agr., Bull. 16, 1SS7, 51.

l84 AIR, WATER, AND FOOD

heating with sulphuric acid, the use of mercury being absolutely
necessary in this case to secure the complete transformation. It
is true also that certain other nitrogenous bodies, notably the
alkaloids and certain organic bases, do not yield all their nitro-
gen to the Kjeldahl process without modifications which com-
plicate the method. For a discussion of the efi&ciency of these
various modifications the student is referred to a paper by
Sherman and Falk.* In the case of cereals, however, and with
the majority of food products, the simpler method outlined will
prove entirely satisfactory.

The per cent of proteids may be found by multiplying the
per cent of nitrogen by an appropriate factor, the one in general
use being 6.25. Recent work has shown, however, that most
of the proteids of cereals contain more than 16 per cent of
nitrogen, so that the factor 6.25 gives results that are too high.
Because all the older work was calculated on this factor, it is
still generally used, nevertheless.

Kjeldahl-Gunning Method. — The Gunning method can be
used in all cases where the Kjeldahl-Wilfarth modification, just
described, is employed, and in some ways it is simpler.

The digestion and distillation are carried out as described on
page 182, using the same amount of sample, together with 20 c.c.
of concentrated sulphuric acid and 10 grams of powdered potas-
sium sulphate. No mercury and, consequently, no potassium
sulphide is used. 100 c.c. of the potash should be added in-
stead of 50.

Note. — The potassium sulphate is added to raise the boiling
point of the sulphuric acid and thus shorten the time required
for the digestion.

Carbohydrates. — The total carbohydrates, often stated in
analyses as "nitrogen-free extract," may be readily obtained by
subtracting from 100 the sum of the percentages of the other
constituents, viz., moisture, ash, ether extract, and nitrogenous
bodies. In many cases, however, especially with the cooked or
treated cereals and with such classes of cereal preparations as

* J. Am. Chem. Soc, 1904, 1469.

ANALYTICAL METHODS 185

infant or invalid foods, a further study of the carbohydrates is
desirable. These are made up of two general classes: (a) soluble
carbohydrates, including sugars, as sucrose, dextrose and maltose,
dextrin and soluble starch, by the latter term being meant starch
which is soluble in water but still gives the characteristic blue
color with iodine, in distinction from some of the more com-
pletely broken-down forms like dextrin, which no longer give
blue or purple colors with iodine; (b) insoluble carbohydrates, in-
cluding starch, pentosans, lignin bodies, and cellulose. The
three latter occur chiefly in the husk or envelope of the grain
or in the woody fiber of the plant. The pentosans or gums are
distinguished from one another by the formation of specific
sugars upon hydrolysis with acids. For ordinary analytical
purposes it is sufficient to determine the lignin and cellulose to-
gether as "crude fiber." Since the exact procedure to be fol-
lowed in the determination of the carbohydrates varies largely
with each specific case, only a general outhne can be presented
here.

Sugars. — The finely ground material, previously dried and
extracted with ether for the removal of crude fat, is extracted
with 85 per cent alcohol. In the extract the reducing sugars
may be determined by means of Fehling's solution as described
on page 145, and the sucrose determined in the same way after
inversion with hydrochloric acid.

Dextrin and Soluble Starch. — The residue from the extrac-
tion of the sugars is treated for eighteen to twenty-four hours
with water at laboratory temperature with frequent agitation,
made up to definite volume, and filtered. This may be tested
with iodine, and if no blue color is produced, evaporated to small
volume, and the dextrin converted to dextrose by dilute hydro-
chloric acid and determined by FehUng's solution. In some few
cases, however, a blue color with iodine may indicate the presence
of soluble starch, in which case an aliquot part of the filtrate may
be treated with an excess of barium hydroxide to precipitate
the starch. In the filtrate from this precipitate the dextrin is
determined by inversion and copper reduction as before. The

l86 AIR, WATER, AND FOOD

difference between the dextrin thus found and the first deter-
mination gives the soluble starch.

Starch. — This may be determined in the residue insoluble in
cold water by digesting it with malt extract, and determining the
dextrose after hydrolysis with dilute acid. It is more common,
however, to determine the starch and other insoluble carbo-
hydrates directly on the original material. The methods for the
determination of starch vary with the condition in which the
starch is found. In the case of nearly pure starch it may be
converted into dextrose by boiling with dilute acid, the dextrose
being then determined by Fehling's solution in the usual way.
Hot acids, however, cannot be used to convert starch in the
natural state, as it is found in cereals, because other carbohydrate
bodies, especially the pentosans, become soluble under these
conditions and the results are too high. In such cases, the
starch is brought into solution by treatment with diastase or by
heating with water under pressure. The results obtained by
direct acid hydrolysis, however, in cases where the highest
accuracy is not required, may be sufficient and the method is
much quicker and easier of execution than the digestion with
diastase.

Direct Acid Hydrolysis. — Directions. — Weigh out from 2 to
5 grams of the sample, depending upon the amount of starch
present, and wash on a filter with five successive portions of
10 c.c. each of ether. Allow the ether to evaporate from the
residue and then wash it with 10 per cent alcohol until free from
soluble carbohydrates. 150 c.c. of the dilute alcohol is generally
sufficient, but if much reducing sugar or dextrin is present, as
may be the case with malted cereals, more will be necessary.
Wash the residue from the filter with 200 c.c. of water into a
500 c.c. graduated flask, add 20 c.c. of hydrochloric acid, sp. gr.
1. 1 25, place a funnel in the neck of the flask to retard evapo-
ration, and heat in a boiling water-bath for two and one-half
hours. Cool, nearly neutralize with sodium hydroxide and
make up to 500 c.c. Filter, and determine dextrose in an
aliquot portion, 25 or 50 c.c. of the filtrate, using the method de-

ANALYTICAL Mf:THODS 187

scribed on page 145. Convert dextrose to starch by the factor
0.9.

Note. — The washing to remove soluble carbohydrates is per-
formed with dilute alcohol rather than with water, because the
former is less likely to carry starch granules through the paper.
The sugar solution when added to the Fehling's solution should
be clear and only faintly acid. It should, in general, contain
not more than 0.5 per cent of reducing sugar.

Determination with Diastase. — Directions. — Treat 2 to 5
grams of the sample with ether and dilute alcohol, as in the
previous method, and wash the residue into a 250-c.c. flask
with 50 c.c. of water. Heat slowly to boiling, or immerse the
flask in boiling water, until the starch gelatinizes, stirring con-
stantly to prevent the formation of lumps. Cool to 55° C, add
20 to 40 c.c. of malt extract, and keep the solution within two
degrees of the stated temperature for an hour or until the solu-
tion no longer gives the starch reaction with iodine under the
microscope. In either case, heat the solution again to boiling
to gelatinize any remaining starch granules, test again and if
starch is found, cool to 55° C, and treat as before, using a
fresh portion of malt extract. Continue this treatment until,
when carefully examined under the microscope, a drop of the
solution fails to give the iodine reaction for starch. Cool,
make up to 250 c.c. and filter through a dry filter. Transfer
200 c.c. of the filtrate to a 500-c.c. graduated flask, add 20 c.c.
of hydrochloric acid, sp. gr. 1.125, and carry out the determina-
tion as described in the preceding method.

A blank determination must be carried through, using 50 c.c.
of water and exactly the same amount of malt extract as used in
the regular procedure, in ©rder to correct for the cupric reducing
power of the malt extract.

Malt Extract. — Treat 40 grams of fresh coarsely ground malt
several hours with 200 c.c. of w^ater, shaking occasionally.
Filter and add a few drops of chloroform to prevent the growth
of molds.

Notes. — The action of the diastase on the gelatinized starch

l88 AIR, WATER, AND FOOD

is to convert it into maltose and dextrin, that is, into soluble
bodies that can be separated by filtration from the pentosans
and other carbohydrates that give the high results in the direct
acid method. By the action of acid (hydrolysis) the maltose and
dextrin are converted to dextrose.

The determination should, if possible, be carried through
without interruption. In case this cannot be done, saHcylic acid
may be used to prevent fermentation, not adding it, however,
until after the digestion with diastase.

If the malt itself is not readily procurable, certain forms of
prepared diastase are on the market and may be found more
convenient either for analytical use or for purposes of illustration.
When possible, however, it is preferable to use the freshly pre-
pared malt extract, as the prepared diastase, made at different
times and from separate portions of malt, may show great differ-
ences in hydrolytic power.

It is sometimes convenient to use freshly collected saliva,
this being free from carbohydrate. In this case, the digestion
should be carried out at 38° C. instead of 55° C.

Crude Fibre. — The Weende method, the one adopted by the
Association of Official Agricultural Chemists, is based on the
assumption that the starch and other digestible carbohydrates
and protein will be removed from the cereal by successive di-
gestion at a boiling temperature with acid and alkali of a definite
strength. The complex body thus obtained is not a definite
chemical compound, but may be considered as being composed
largely of cellulose.

Use 2 grams of the finely-ground sample and wash on a filter
with 5 portions of 10 c.c. each of ether. (The residue from the
determination of "ether extract" can be used if desired.)

Transfer the washed material to a 500-c.c. Erlenmeyer flask,
add 200 c.c. of boihng 1.25 per cent sulphuric acid, place a
funnel in the neck of the flask and boil gently for 30 minutes.
Filter on a ribbed filter and wash with several portions of boiling
water. Transfer the precipitate by means of 200 c.c. of boiling
1.25 per cent sodium hydroxide in a small wash-bottle to the

ANALYTICAL METHODS 1 89

same 500-c.c. Erlenmeyer flask, and boil again gently for 30
minutes.

Filter on ignited asbestos in a Gooch crucible, wash with
boiling water until free from alkali, then with 10 c.c. of alcohol,
and finally with 10 c.c. of ether. Dry at the temperature of
boiling water to constant weight. Ignite carefully at first, then
at a low red heat until the organic matter is destroyed. Calcu-
late the loss on ignition as "crude fibre."

Note. — The filtration will be found to proceed fairly rapidly
if the solution is filtered hot and care is taken to keep the residue
from the filter as long as possible.

The sulphuric acid and sodium hydroxide should be carefully
prepared and the strength determined by titration.

Examination of Malted Cereals. — The relation of the carbo-
hydrates in a malted cereal, which ordinarily consist of maltose,
dextrin and starch, may be readily learned by the following
simple analytical scheme, due to Sherman.*

Directions. — Mix 5 grams of the ground sample with 125 c.c.
of cold water in a 250-c.c. graduated flask and allow it to stand
at room temperature for an hour, shaking frequently. Make
up to the mark, mix and filter through a dry filter. Determine
the reducing sugar in 25 c.c. of the filtrate as described on page
145, and calculate as maltose in the original sample. Measure
50 c.c. of the same filtrate into a loo-c.c. flask, add 5 c.c. of
hydrochloric acid (sp. gr. 1.12), and hydrolyze as directed on
page 186. Filter and determine the dextrose in the filtrate as
on page 145. Subtract the amount due to maltose and calculate
the remainder to dextrin by multiplying by 0.9.

Treat another portion of the original sample as described un-
der the determination of starch by acid hydrolysis, page 186,
without, how^ever, extracting the soluble carbohydrates. From
the dextrose found subtract that given by dextrin and maltose
and calculate the remainder to starch.

Notes. — The presence of undissolved material in the flask
when diluted to volume renders the result somewhat inaccurate,

* Methods of Organic Analj'sis, 2d Ed., p. 341.

I go AIR, WATER, AND FOOD

and the possible presence of other reducing sugars than maltose
introduces error, but the results are sufficiently close for com-
parative tests.

Examination of Fermented Liquors

WINE

General Statements. — The object of a wine analysis is ordi-
narily to determine whether or not a wine is pure and un-
adulterated, or whether it has been properly made. Special
works furnish sufficient information concerning processes of
manufacture, and it is essential to know here only the general
composition of the grape- juice or "must" and how, by the
natural process of fermentation, this may be altered in the
finished product.

The "must" contains sugars (mainly dextrose); dextrin;
organic acids and salts, mainly tartaric and malic acids; salts of
inorganic acids, chiefly phosphates, sulphates, and chlorides.
Various extractive matters, which largely affect the color and flavor
of the wine, together with a little tannin and albuminous sub-
stances, are also present. The wine will contain, then, besides
water, the following: Alcohol, glycerine, frequently some sugar
that has escaped fermentation, ethers, which determine largely
the "bouquet" of the wine, and more or less of the acids, salts,
coloring and extractive matters of the must, together with vary-
ing amounts of carbonic, acetic, and succinic acids.

According to differences in their composition, wines may be
divided into various classes, such as "dry" wines, which contain
very little sugar, as distinguished from the sweet wines, in which
a notable quantity of sugar has escaped fermentation, or to
which an addition of sugar has been made subsequent to the
main fermentation. Or they may be divided according to the
content of alcohol into natural wines and those fortified by ad-
dition of alcohol, as port, sherry, and madeira.

The composition of the wine may be changed, moreover, by
the various methods which are used for its "improvement,"

ANALYTICAL METHODS 191

such as fortification already mentioned, plastering, petioiization,
etc. Information regarding these methods will be found in
some of the larger works mentioned in the bibliography.

Determinations of value in judging the purity of wine are
alcohol, glycerine, extract, ash, total and volatile acids. The
actual percentages of these substances are not of so great value as
certain relations between them, such as the ratio of ash to extract,
extract to alcohol, alcohol to glycerine, alcohol to acids, and
volatile to total acids. Examination for preservatives and for-
eign coloring matters should also be made. It should, perhaps, be
stated that the analytical procedure given here is to furnish
practice in the examination of a fermented food product, and is
by no means as thorough as might be needed to judge the quaHty
or genuineness of a wine.

Specific Gravity. — This is to be taken by means of the
pyknometer at 15^.5 C.

Notes. — Where the specific gravity of the sample is known,
the various portions taken for analysis can be more conven-
iently measured than weighed. The results can be calculated
to per cent by weight by dividing the results expressed as grams
per 100 c.c. by the specific gravity.

Effervescing wines should, before analysis, be vigorously
shaken in a large flask to hasten the escape of carbon dioxide.
The liquid may then be poured from under the foam into an-
other vessel.

Alcohol. — Principle. — The alcohol is obtained freed from
everything but water, and its amount determined by ascertain-
ing the specitic gravity of the mkture, and taking the per cent
from the tables.

Directions. — Measure (or weigh) 100 c.c. of the wine into a
500-c.c. round-bottomed flask. Add 50 c.c. of water and if the
wine is very acid a small pinch of precipitated calcium carbon-
ate. With most wines this addition will not be necessary.
Distill about 95 c.c. into a loo-c.c. graduated flask. Fill to the
mark with distilled water, mix thoroughly, and take the specific
gravity of the distillate at 15.5° C. with a pyknometer. The per-

192 AIR, WATER, AND FOOD

centage of absolute alcohol by volume corresponding to the
observed density will be found in Table X, page 217.

To find the alcohol by weight in the sample, multiply the per
cent of alcohol by "weight in the distillate as taken from the table,
by the weight of the distillate and divide the result by the
weight of the sample used.

Notes. — The addition of calcium carbonate is to prevent the
distillation of acetic acid. A certain amount of volatile ethers
may also pass over into the distillate, but it is so slight that its
influence may be neglected.

Normal wines ordinarily contain between 4.5 and 12 per cent of
alcohol except in the case of "fortified" wines, where the amount
may be even 20 per cent. Fermentation does not yield more
than about 14 per cent of alcohol.

Extract. — The method to be employed depends on the pro-
portion of extract. A preliminary calculation should be made
by the aid of the formula

X = 1 -{- d — d',
where x is the specific gravity of the dealcoholized wine, d the
specific gravity of the wine, and d' the specific gravity of the
distillate obtained in the determination of alcohol. The value
for X is found from Table XI, page 220.

Dry Wines. — (Having an extract content of less than 3 per
cent.) Evaporate 50 c.c. on the water-bath to a sirupy con-
sistency in a flat-bottomed platinum dish. Heat the residue in
the oven at 100° C. for two hours and a half, cool in a desiccator
and weigh.

Sweet Wines. — When the extract content is between 3 and
6 per cent treat 25 c.c. of the sample as described under dry
wines. When the amount of extract exceeds 6 per cent it is best
to accept the result found from the table and not to determine
it gravimetrically.

Notes. — The gravimetric determination will be inaccurate
with wines high in extract on account of the serious error caused
by dr>ing levulose at high temperatures. The figures in the
table are based on determinations made at 75° C. in vacuo.

ANALYTICAL METHODS 1 93

Wine made from the juice of ripe grapes rarely contains less
than 1.5 per cent of extract in the case of white wines and about
2.0 per cent in the case of red wines. The amount of extract
decreases of course with age.

Alcohol-extract Ratio. — The municipal laboratory of Paris
considers a wine "fortified" if the alcohol exceeds 4.5 times the
extract for red wines and 6.5 for white wines. The extract and
alcohol should both be expressed in per cent by weight. The
amount of added alcohol is calculated by the municipal labora-
tory by subtracting the "natural" alcohol (extract X 4.5 or 6.5)
from the total alcohol.

Ash. — Ignite the residue from the extract determination as
described on page 180.

Note. — The amount of ash in a natural wine averages about
10 per cent of the extract, varying ordinarily between 0.14 per
cent and 0.35 per cent.

Glycerine. — The determination of glycerine, and the ratio
of glycerine to alcohol is of much value in judging the purity of
a wine. The determination of the glycerine, however, is rather
difficult and requires some little experience in order to obtain
good results. The official method of the Association of Agri-
cultural Chemists will be found in Bur. of Chem., Bull. 107,
(Rev. Ed.), p. 83. A more accurate modification, however, is
that of Ross {Bull. 132, p. 85).

Free Acids: Total Acidity Calculated as Tartaric Acid. —

Measure 25 c.c. of the wine into a small beaker, heat just below

... . . N

the boilmg pomt to expel carbon dioxide, and titrate with —

sodium hydroxide and phenolphthalein. In the case of red

wines use delicate red litmus paper, taking the end-point when

a drop of the liquid placed upon the paper produces a blue spot

in the middle of the portion moistened. Calculate the results as

N
tartaric acid. One c.c. — ■ sodmm hydroxide = 0.007^ gram of

tartaric acid.

194 AIR, WATER, AND FOOD

Volatile Acids Calculated as Acetic Acid. — Measure 50 c.c.

of wine into a 300-c.c. flask provided with a cork having two

perforations. One is fitted with a tube 6 mm. in diameter and

blown out to a bulb 40 mm. in diameter a short distance above

the cork; this tube is connected with a condenser. The other

perforation carries a tube reaching nearly to the bottom of the

flask and drawn out to a small aperture at its lower end ; this is

connected with a 500-c.c. flask containing water. Heat both

flasks to boiling; then lower the flame under that containing the

wine, adjusting the flame so that the volume of liquid remains

constant, and continue the distillation by means of steam until 200

. N .
c.c. have distilled. Titrate the distillate with — - sodium hydrox-

ide, using phenolphthalein as an indicator. Calculate the results

N
as acetic acid. One c.c. — sodium hydroxide = 0.0060 gram

of acetic acid.

Hortvet * has described a compact self-contained apparatus
for determining the fixed and volatile acids in which the wine is
surrounded by boihng water while the steam is being passed
through, giving excellent results.

Fixed Acids Calculated as Tartaric Acid. — These may be
found by calculating the volatile acids as tartaric and sub-
tracting the result from the total tartaric acid found by direct
titration.

Note. — The total acids in a wine vary usually between 0.45
per cent and 1.5 per cent. The acid content is frequently
diminished by aging or by the separation of cream of tartar.
The volatile acid should, in general, not be over 0.12 to 0.16
per cent, depending upon the age of the wine. A wine properly
made should not have the volatile acid, estimated as acetic, ex-
ceed one-fourth of the total free acid, calculated as tartaric.

Coloring Matters: Detection of Coal-tar Dyes.j — Fifty c.c.
of the sample are diluted to 100 c.c. with water, filtered if neces-

* /. hid. Eng. Chem., 1910, 31.

t Sostegni and Carpentieri: Zlschr. anal. Chem., 35, i8g6, 397.

ANALYTICAL METHODS 1 95

sary, faintly acidified with hydrochloric or acetic acid, and a
piece of white woolen cloth, which has been thoroughly washed
with hot water, is immersed in the solution and boiled for five to
ten minutes. The cloth is then removed and thoroughly washed
with boiling water, and boiled in a dilute solution of ammonia
(i : 50). With some of the dyes the color is stripped from the
wool quite readily; with others it is necessary to boil for some
time. The wool is removed, the ammoniacal solution made
faintly acid with hydrochloric acid, and another piece of white
wool is immersed and again boiled. This second dyeing fixes
coal-tar dyes on the fibre, but fruit and vegetable colors remain
on the first piece of wool.

Notes. — It is absolutely necessary that the second dyeing
should be made, as some of the coal-tar dyes will dye a dirty
orange in the first acid bath which might be easily passed for
vegetable color but on treatment in alkaline bath and second
acid bath becomes a bright pink.

Excess of acid should be avoided since some of the colors do
not dye readily in strongly acid solution.

Another advantage in the second dyeing is that if a large
piece of woolen cloth is used in the first dyeing, and a small
piece in the second dyeing, small amounts of coloring matter
can be brought out much more decidedly in the second dyeing,
where practically all of the vegetable coloring matter has been
excluded.

Several colors which are not coal-tar dyes, notably archil and
archil derivatives, give reactions b}' this method and are liable
to be confused with coal-tar colors. For hints as to the method
for detecting these reference may be made to Bulletin 107,
Bureau of Chemistry, page 190.

The further separation and identification of the artificial
colors is too difficult a matter to be taken up here. The student
is referred for information on this point to the following: ]\Iulli-
ken: The Identification of Commercial Dyestuffs; Loomis:
Circular 63, Bureau of Chemistry; Allen: Commercial Organic

196 AIR, WATER, AND FOOD

Analysis, 4th Ed., Vol. V; Green and others*: The Identi-
fication of Dyestuffs on Animal Fibres.

Preservatives. — The preservatives to be sought generally in
wines are salicylic and benzoic acids and their salts. Sulphurous
acid and sulphites are also used. For methods of detecting
other substances less commonly employed, such as abrastol, beta-
naphthol, etc., reference may be made to Bulletin 107 of the
Bureau of Chemistry. Boric acid is occasionally used, but since
a small amount of it is normally present in wines, tests, to be
of value, should be quantitative.

Salicylic Acid. — Acidify about 50 c.c. of the wine with 5 c.c.
of dilute (i : 3) sulphuric acid and extract in a separatory fun-
nel with 25 c.c. of ether. Draw off the lower layer, wash the
ether twice with water, using 10 c.c. each time and finally evapo-
rate the ether in a porcelain dish at room temperature. To the
residue in the dish add 2 to 3 drops of very dilute ferric chloride
or better ferric alum solution (App. B). A deep purple or violet
color indicates salicylic acid.

Notes. — Not more than 50 c.c. should be used for the test,
since a trace of salicylic acid seems normally present in some
wines.

The washing with water is to free the ether from traces of
sulphuric acid which interferes with the development of the
violet color.

Care should be exercised in making the extraction with ether
not to shake the separatory funnel too violently, since a trouble-
some emulsion may result.

Benzoic Acid.\ — Acidify about 100 c.c. of wine with sulphuric
acid, extract with ether, and evaporate the ethereal solution as
in the detection of salicyKc acid. Treat the residue with 2 or
3 c.c. of strong sulphuric acid. Heat till white fumes appear;
organic matter is charred and benzoic acid is converted into
sulpho-benzoic acid. A few crystals of ammonium nitrate are
then added. This causes the formation of metadinitrobenzoic

* /. Soc. Dyers attd Colourists, 190 j, 236.
t Mohler: Bull. Soc. Chim. [3], 3, 1890, 414.

ANALYTICAL METHODS I97

acid. When cool the acid is diluted with water and ammonia
added in excess, followed by a drop or two of ammonium sulphide.
The nitro-compound becomes converted into ammonium meta-
diamidobenzoic acid, which possesses a red color. This reaction
takes place immediately, and is seen at the surface of the liquid
without stirring.

Sulphurous Acid and Sulphites. — See directions under Beer,
page 198.

BEER AND OTHER IVLA.LT LIQUORS

Before analysis the sample must be thoroughly shaken in a
large flask, in order to remove carbon dioxide.

Specific Gravity. — Taken with a pyknometer at 15.5° C.

Alcohol. — Determined as in the analysis of wine. The ad-
dition of calcium carbonate will not be necessary. If the sample
foams much this can be prevented by the addition of about half
a gram of tannin before distilling.

Extract. — Determine the extract content corresponding to
the specific gravity of the dealcoholized beer according to Table
XIII. For this purpose employ the formula

Sp = g + {i~g'),

in which Sp is the specific gravity of the dealcoholized beer, g
the specific gravity of the beer, and g' the specific gravity of the
distillate obtained in the determination of alcohol. Instead of
using this formula the residue from the distillation of alcohol is
sometimes diluted to the original volume, and its specific grax'ity
taken. This is often impracticable owing to the necessity of
employing tannic acid to prevent foaming in the distilling flask,
and owing to the coagulation of proteids during the distillation.

Note. — • The extract of beer cannot be accurately determined
by evaporation and drying at the boiling-point of water because
of the dehydration of the maltose.

Ash. — -Evaporate 25 c.c. to dryness and determine as de-
scribed on page 180.

Free Acids. — Heat 20 c.c. to incipient boiling to expel carbon
dioxide and titrate as in the analysis of wine. Fixed acids, con-

198 AIR, WATER, AND FOOD

sisting principally of lactic and succinic, are calculated as lactic

N . .

acid. One c.c. of — ■ sodium hydroxide = 0.0090 gram of lactic
10

acid.

Reducing Sugar. — Dilute 25 c.c. of the beer, freed from car-
bon dioxide, to 100 c.c. Determine the reducing sugar in 25 c.c.
of this solution as directed on page 145, enough water being
added to make the total volume of the Fehling's solution-sugar
mixture 100 c.c. Express the results in terms of maltose, as
given in Table XII.

Preservatives. — The preservatives most commonly employed
in beer are benzoic and salicylic acids and their sodium salts,
sulphites and fluorides.

Benzoic and Salicylic Acids. — Detected as described under
Wine.

Sulphites. — Qualitative Test. — Use an apparatus similar to
that described for the determination of volatile acids in wine.
To 50 c.c. of the sample add about a gram of sodium bicarbonate,
20 c.c. of 20 per cent phosphoric acid, and immediately con-
nect the flask with the condenser. Pass steam through the
flask until about 20 c.c. have collected in the distillate. To the
distillate add bromine water in slight excess and boil. Expel
the excess of bromine and test for sulphuric acid with hydro-
chloric acid and barium chloride in the usual manner.

Notes. — The method described does not distinguish between
free sulphurous acid and that present in the form of sulphites.
The former can be distilled without the addition of phosphoric
acid.

The presence of sulphites in a sample should not be con-
sidered e\idence of added preservatives unless an excessive
amount is found, since the use of sulphured malt or hops may
introduce a small amount. To obtain conclusive data, a quan-
titative determination of the amount present should be made.

This can be done by a method similar to that used for its
detection, distilling in a current of carbon dioxide, absorbing
the sulphur dioxide in bromine water and determining the re-

ANALYTICAL METHODS 199

suiting sulphuric acid as barium sulphate. In the case of food
products, where sulphides are liable to be present also, the steam
should pass through a solution of copper sulphate* before en-
teriiog the condenser in order to remove any hydrogen sulphide
formed by the action of the phosphoric acid. Details of the
method will be found in Leach's Food Analysis.

In Bulletin 107 it is recommended to distill into a standard
iodine solution and titrate the excess of iodine. This has the
disadvantage, however, that other iodine-reducing substances
than sulphurous acid may pass into the distillate and give too
high results.

Fluorides. — The well-known cjualitative test for fluorides by
etching a glass plate may be modified by the use of a suitable
condenser and made sufficiently delicate to be used here. It is
possible also by suitable regulation of the temperature to make
the test approximately quantitative.!

Flavoring Extracts

The work on alcoholic liquids can be pleasantly varied by
substituting for it, in some cases, the determination of alcohol
and other important components of the usual flavoring essences',
the most important of which are vanilla and lemon. Several
important types of analytical methods, such as the determina-
tion of essential oils and quantitative extraction with volatile
solvents, are also brought to the attention of the student.

VANILLA

Vanilla extract is a dilute alcoholic tincture of the vanilla
bean, the fruit of a climbing plant of the orchid family. The
best grades are made by allowing the cut and bruised beans to
macerate in the alcohol for several months, the liquid thus
obtained being deep brown in color, with a delightful perfume
and flavor. Sugar is added to assist in the extraction and to
sweeten the product.

* Winton and Bailey: J . Am. Chcm. Soc, igoy, 1499.

t Woodman and Talbot: /. Am. Chem. Soc, igo6, 1437; 1907, 1362.

200

AIR, WATER, AND FOOD

The cost of a quart of the pure extract, according to Winton,*
is from about 60 cents to $2.50, depending chiefly upon the
grade of beans used.

The composition of five pure vanilla extracts, made from
beans of different grades, is given in the following table,t the
results being expressed in per cent by weight:

Grade of bean.

Specific
gravity.

Vanillin.

Alcohol.

Total
residue.

Cane-
sugar.

Mexican (whole)

Mexican (cut)

South American (whole) .

Bourbon (whole)

Tahiti (whole)

I. 0159
I. 0146
I . 1009
I. 0166
I .0104

0.125
0.065
0.215
0.138
0.108

37-96
39-92
38.58
38-32
38-84

22.60
23.10
22.00
23-13
21-75

19.90
19.20
19.00
20.40
20.00

The adulteration of vanilla extract consists principally in the
use of extract of Tonka bean, a cheap substitute somewhat re-
sembling vanilla in its flavor, in the use of artificial prepara-
tions of the active principles of vanilla and tonka, vanillin and
coumarin, and in the addition of artificial color, usually cara-
mel. A cheap extract may be entirely an artificial mixture,
made of artificial vanillin or coumarin, or both, in weak alcohol,
colored with caramel. An occasional adulteration is the use of
alkali, such as potassium bicarbonate, to hold the resin in solu-
tion and permit the use of a more dilute alcohol.

An extract of vanilla of good quality should contain from 25
to 40 per cent of alcohol, from o.io to 0.20 per cent of vanillin,
and give a good precipitate of vanilla resins. Imitation extracts
usually show one or several of the following characteristics:
Presence of coumarin; deficiency in resins; abnormally low or
high content of vanillin; presence of artificial color; low lead
number.

Analytical Methods. — Alcohol. — Measure 25 c.c. of the
sample, add 100 c.c. of water, and determine the alcohol by

* Conn. Agr. Exp. Sta. Report, igoi, 150.
t Conn. Agr. Exp. Sta. Report, igoi, 150.

ANALYTICAL METHODS 20I

volume, as directed on page 191, omitting the use of calcium
carbonate and tannic acid.

Vanillin and Coumarin. — (Modified method of Hess and
Prescott).* Weigh 50 grams into a 250-c.c. beaker with marks
showing volumes of 80 c.c. and 50 c.c, dilute to 80 c.c, and
evaporate to 50 c.c. in a water-bath kept at 70° C. Dilute again
to 80 c.c. and evaporate to 50 c.c. Transfer to a loo-c.c. flask,
rinsing out the beaker with hot water, add 25 c.c. of lead acetate
solution (80 grams of neutral lead acetate made up to a liter),
make up to the mark with water, shake and allow it to stand
over night. Decant on a small dry filter, pipette off 50 c.c. of
the filtrate, and extract it four times in a separatory funnel,
using 15 c.c. of ether each time.

Combine the ether extracts in another separatory funnel and
wash five times wdth 2 per cent ammonium hydroxide, using
10 c.c. the first time and 5 c.c. for each subsequent shaking. Set
aside the combined ammoniacal solutions for the determination
of vanillin.

Transfer the ether solution to a weighed dish and allow the
ether to evaporate at room temperature. Dry in a desiccator
over sulphuric acid and weigh. If the residue is not white and
crystalline stir it for fifteen minutes with 15 c.c. of petroleum
ether (boiling point 30° to 40° C.) and decant the clear liquid into
a beaker. Repeat the treatment with petroleum ether two or
three times. Allow the residue to stand in the air until ap-
parently dry, completing the drying in the desiccator. Weigh,
and deduct the weight from the weight of the residue obtained
after the ether evaporation, thus obtaining the weight of the
coumarin. This may be recognized by its characteristic odor,
resembling that of "sweet grass," and by Leach's testf as
follows: Dissolve the residue in a few drops of hot water,

N . .
and add one or two drops of — iodine in potassium iodide.

On stirring with a rod, a brown precipitate will form, which

* /. Atn. Chem. Soc, igo^, 719; Bur. of C hem., Bull. 137, 68.
t Leach: "Food Inspection and Analysis," 3d Ed., p. 867.

202 AIR, WATER, AND FOOD

will gather into dark green flocks. The reaction is especially
marked if carried out in a white porcelain crucible or dish.

Slightly acidulate the ammoniacal solution reserved for vanillin
with lo per cent hydrochloric acid. Cool, and shake out in a
separatory funnel with four portions of ether, as described for
the first ether extraction. Evaporate the ether at room tem-
perature in a weighed dish, dry over sulphuric acid, and weigh
the vanillin.

If the residue is white, it may be safely assumed, in the majority
of cases, that it is pure vanillin. If dark colored, however, the
dry residue should be extracted not less than fifteen times with
boiling petroleum ether (boiling point 40° C. or below) . Evapo-
rate the solvent, dry and weigh the vanillin. A small amount
of the residue, dissolved in two drops of concentrated hydro-
chloric acid, should give a pink color upon the addition of a
crystal of resorcin.

Notes. — The separation of vanillin and coumarin is based
on the differences in their chemical constitution. VaniUin is
hydroxymethoxybenzoic aldehyde, while coumarin is the anhy-
dride of orthohydroxycinnamic acid. On account of the alde-
hydic nature of the vanillin, the separation by dilute ammonia
is possible, the aldehyde ammonia compound of vanillin being
readily soluble in water, while the coumarin remains wholly in
the ether.

If a portion of the vanilHn, after weighing, be dissolved in two
or three drops of ether and allowed to evaporate spontaneously
on a microscope sHde it shows a characteristic appearance with
polarized light. The vanillin crystallizes in slender needles,
forming star-shaped clusters. These give a brilliant play of
colors with crossed Nicols, even without the selenite plate.

Normal Lead Number. — To a lo-c.c. portion of the filtrate
obtained from the lead acetate in the determination of vanillin
and coumarin add 25 c.c. of water, sulphuric acid in slight excess,
and 100 c.c. of 95 per cent alcohol, let stand over night, filter on a
Gooch crucible, wash with alcohol, dry in the oven of the water-
bath, ignite for three minutes at low redness, taking care to

ANALYTICAL METHODS 203

avoid the reducing flame, and weigh the lead sulphate. Cal-
culate the normal lead number by the following formula

p ^ 100 X 0.6831 {S - W)
5

in which P = normal lead number, 5 = grams of lead sulphate

corresponding to 2.5 c.c. of the lead acetate solution, as deter-
mined from a blank analysis, and W = grams of lead sulphate
obtained in 10 c.c. of the filtrate, as just described.

Note. — The normal lead number of genuine vanilla extracts
determined by this method ranges from 0.35 to 0.60. Artificial
extracts generally are distinctly lower, sometimes as low as 0.03,

More accurate results can be obtained by regulating more
closely the time and temperature during the standing of the so-
lution with lead acetate. Winton and Berry* recommend stand-
ing 18 hours at 37° to 40° C. They find that, determined in this
manner, the minimum normal lead number for vanilla extracts
prepared according to the U. S. Pharmacopoeia is 0.40.

Resins. — Evaporate 25 or 50 c.c. of the extract to one-third
its volume on the water-bath in order to remove the alcohol.
Make up to the original volume with hot water. If no alkali
has been used in the manufacture of the extract, the resin
should appear at this point as a flocculent brown residue. Add
acetic acid in slight excess, allow the evaporating-dish to stand
in a warm place for a time to separate the resin completely,
and filter. Wash the residue on the filter, and save both the
filtrate and residue. Test the resin by placing pieces of the
filter, with the resin attached, in a few cubic centimeters of
dilute caustic potash. The resin is dissolved with a deep red
color, and on acidifying is again precipitated. Test the filtrate
by adding to it a few drops of basic lead acetate. A bulky pre-
cipitate is formed, on account of the organic acid, gums, etc.,
present.

Confirm the resin test by shaking 5 c.c. portions of the ex-
tract in separate test-tubes with 10 c.c. of amyl alcohol and

* Bur. of C hem., Bull. 137, 120.

204 AIR, WATER, AND FOOD

lo c.c. of ether. With pure extracts the upper layers will be
colored, varying from light yellow to deep brown; with artificial
extracts, free from resin, the amyl alcohol and ether layers will
be uncolored.

Note. — While the artificial vanillin, as sold on the market
and used in the manufacture of low-grade extracts, is identical
with the vanillin of the vanilla bean, it is true that pure extracts
owe their value and flavor to other ingredients as well as to the
vanillin present. Among these "extractive matters" the resins
are important from an analytical standpoint, serving by their
presence or absence to determine whether true vanilla is present
or the extract entirely artificial. As a quick and ready test,
serving to distinguish artificial extracts from genuine prepara-
tions of the vanilla bean, the amyl alcohol and ether tests will
be found especially useful.

Color : Caramel. — Caramel is the color commonly used in
vanilla extracts, although coal-tar dyes have been found. The
presence of dyes is sometimes indicated by the color of the
amyl alcohol in testing for the resin, they being in many cases
soluble in amyl alcohol, but insoluble in ether.

Lead Acetate Test. — The coloring matter present in vanilla
extracts is almost completely removed when the dealcoholized
extract is treated with a few cubic centimeters of basic lead
acetate solution. When caramel is present, the filtrate and
precipitate, if any, have the characteristic red-brown color of
caramel.

Marsh Test.* — Evaporate 25 c.c. of the extract until the odor
of alcohol is no longer apparent and the liquid is reduced to a
thick sirup. Dissolve the residue in water and alcohol, using
26.3 c.c. of 95 per cent alcohol, and making up to volume in a
50-c.c. flask with water. Transfer 25 c.c. of this solution to a
separatory funnel; add 25 c.c. of the Marsh reagent and shake,
not too vigorously, to avoid emulsification. Allow the layers
to separate and repeat the shaking twice more. After the
layers have separated clearly, run off the lower layer into a 25-c.c.

* Bur. of Chem., Bull. 152, p. 149.

ANALYTICAL METHODS 205

cylinder, and make up to volume with 50 per cent (by volume)
alcohol. Filter if necessary and compare in a colorimeter with
the remaining 25-c.c. portion (which has not been extracted with
the reagent) and express the results as per cent of color insolu-
ble in amyl alcohol.

The Marsh reagent is prepared as follows: Mix 100 c.c. of
amyl alcohol, 3 c.c. of sirupy phosphoric acid, and 3 c.c. of water;
shake before using. If the reagent becomes colored on standing,
the amyl alcohol should be redistilled over 5 per cent phosphoric
acid.

Note. — The method is based on the greater solubility in acid
amyl alcohol of the natural color of the vanilla bean as com-
pared with caramel. A genuine extract, uncolored with caramel,
will not usually show more than 40 per cent of color insoluble in
amyl alcohol.

LEMON

Lemon extract is usually made by dissolving oil of lemon,
obtained by expression or distillation from the rind of the lemon,
in strong alcohol. The product is sometimes colored with the
color of lemon peel. The Federal standards * require a content
of lemon oil of at least 5 per cent by volume. The expensive
ingredient of the extract is the alcohol, since alcohol of at least
80 per cent strength by volume must be used to dissolve 5 per
cent of lemon oil; hence in making cheap extracts the manu-
facturer endeavors to use a dilute alcohol, even under the neces-
sity of omitting a portion or all of the oil of lemon.

The common forms of adulteration of lemon extract are the
use of weak alcohol and consequent deficiency of lemon oil, as
already noted ; the substitution for the lemon oil of small amounts
of stronger oils, as oil of citronclla, oil of lemon-grass, and the
like; the use of citral, the odorous principle of lemon oil, used
for making the so-called "terpencless lemon extracts;" and the
coloring of the extracts by coal-tar colors or turmeric.

Preliminary Test. — To a little of the extract in a test-tube
add seven or eight times its volume of water. A high-grade ex-
* U. S. Dcpt. -Agric, OfBce of the Secretary, Circ. 19.

206 AIR, WATER, AND FOOD

tract will show a heavy cloud, due to the precipitation of the
lemon oil. If no cloudiness or turbidity appears it may be safely
inferred that no oil is present.

Alcohol. — The determination of alcohol is somewhat com-
plicated in this case by the presence of the volatile oil of lemon
which must be removed before distilling.

Dilute 20 c.c. of the extract to 100 c.c. with water, and pour
the mixture into a dry Erlenmeyer flask containing 5 grams of
light magnesium carbonate. Shake thoroughly and filter
through a dry filter. Measure 50 c.c. of the clear filtrate, add
about 15 c.c. of water, and distill 50 c.c, as directed on page 191.
From the specific gravity of the distillate determine the per cent
of alcohol by volume, and this, multiplied by 5, will give the
percentage in the original extract.

Note. — The magnesia serves to absorb the precipitated oil
and prevent it from passing through the filter.

Lemon Oil. — Pipette 20 c.c. of the extract into a Babcock
milk bottle; add i c.c. dilute hydrochloric acid (i : i); then
add from 25 to 28 c.c. of w'ater previously warmed to 60° C;
mix and let stand in water at 60° for five minutes; whirl in
centrifuge for five minutes; fill with warm water to bring the
oil into the graduated neck of the flask; repeat whirling for
two minutes; stand the flask in water at 60° C. for a few min-
utes and read the per cent of oil by volume. If the determina-
tion is not made in duplicate the flask should be balanced by
another containing an equal weight of water. In case oil of
lemon is present in amounts over 2 per cent add to the percent-
age of oil found 0.4 per cent to correct for the oil retained in
solution. If less than 2 per cent and more than i per cent is
present, add 0.3 per cent for correction.

Color. — Test for coal-tar colors by evaporating a portion of
the extract to dryness on the water-bath. Dissolve the residue
in water and carry out the double dyeing method, as described
on page 194.

It may be advisable not to add any acid to the dye bath, as
Naphthol Yellow S, which is commonly used in lemon extracts,
dyes wool best from a nearly neutral bath.

ANALYTICAL METHODS 207

To test for turmeric add to a portion of the sample three
drops of saturated boric acid solution, one Sfnall drop of dilute
(i : 10) hydrochloric acid, and a piece of filter-paper so ar-
ranged that it is only half immersed in the liquid. Evaporate
to dryness on the water-bath. In the presence of turmeric the
paper will be colored pink and the test may be confirmed as
described on page 154. Excess of hydrochloric acid should be
avoided as in testing for boric acid.

To show the presence of natural color derived from lemon
peel the following reactions will be found helpful:* Dilute a few
cubic centimeters of the extract until the color has nearly dis-
appeared and divide the solution between two test-tubes. To
one add a few drops of concentrated hydrochloric acid and to
the other a few drops of strong ammonia. In the presence of
natural color a distinct yellow color should result in each case.

Citral. — See Bur. of C hem., Bull. 137, 70.

* Albrech: Bur. oj Chem., Bull. 137, 71.

APPENDICES

APPENDIX A

TABLE I

TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY FROM O TO 3O.9 C.
REDUCED TO 0° AND SEA-LEVEL

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0°

4-57

4.60

4.64

4.67

4.70

4.74

4.77

4.80

4.84

4.87

4.98

5.02

5.05

5.09

5.12

5-16

5.20

5.23

5-35

5-39

5-42

5 46

5-50

5-54

5.58

5.62

5-74

5.78

5-82

5-86

5-9°

5-94

5. 99

6.03

6. IS

6.20

6.24

6.28

6.33

6.37

6.42

6.46

6.60

6.64

6.69

6.74

6.78

6.83

6.88

6.92

7.07

7.12

7.17

7.22

7.26

7.31

7-36

7.42

7-57

7.62

7.67

7.72

7-78

7.83

7.88

7.94

8.10

8.15

8.21

8.27

8.32

8.38

8.43

8.49

8.66

8.72

8.78

8.84

8.90

8.96

9.02

9.08

9.26

9.32

9.39

9.45

9-51

9.58

9-64

9.70

9.90

9.96

10.03

10.09

10.16

10.23

10.30

10.36

10. S7

10.64

10.71

10.78

10.85

10.92

10.99

11.06

XI. 28

11.36

11.43

11.50

11.58

11.66

11.73

II. 81

12.04

12.12

12.19

12.27

12.35

12.43

12.51

12.59

12.84

12.92

13.00

13.09

13.17

13.25

13.34

13-42

13-68

13-77

13.86

13-95

14.04

14.12

14.21

14.30

14.58

14.67

14.76

14.86

14.95

IS -04

1S-14

15.23

1552

15.62

15-72

15.82

15-92

16.02

16.12

16.22

16.52

16.63

16.73

16.83

16.94

17.04

17-15

17.26

17.58

17.69

17.80

17.91

18.02

18.13

18.24

18.35

18.69

18.81

18.92

19.04

19.16

19.27

19.39

19.51

19.87

19.99

20.11

20.24

20.36

20.48

20.61

20.73

21. II

21.24

21.37

21.50

21.63

21.76

21.89

22.02

22.42

22.55

22.69

22.83

22.96

23.10

23.24

23.38

23.80

23-94

24.08

24-23

24-37

24.52

24.66

24.81

25.25

25 40

25.55

25.70

25.86

26.01

26.16

26.32

26.78

26.94

27.10

27.26

27-42

27.58

27.74

27.90

28.39

28.56

28.73

28.89

29.06

29.23

29.40

29.57

30.09

30.26

30.44

30.62

30.79

30.97

31.15

31-33

31.87

32.06

32.24

32.43

32.61

32.80

32.99

33-18

208

APPENDIX A

209

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APPENDIX A

211

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AIR, WATER, AND FOOD

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MCjrO'i-JOOr^-OOO'OwMr'

5 Tt u-)\0 t^cO 0> O M

APPENDIX A

213

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AIR, WATER, AND FOOD

s o .2

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APPENDIX A

TABLE VII

SULPHATES IN WATER

(Reduced from table in article by H. F. Muer, J. Ind. Eng. Chem., 191 1,

Vol. 3, p. 553)

Depth,

SO3, pts. per

Depth,

SO3, pts. per

Depth,

SOj, pts. per

Depth,

so,, pts. per

cm.

million.

cm.

million.

cm.

million.

cm.

million.

i-S

3130

6.7

72.0

II. 9

47-3

17.1

37-3

280.0

12.0

17.2

250.0

12. I

17-3

238.0

12.2

•5

174

225.0

12.3

•3

175

213.0

12.4

17.6

200.0

12.5

17.7

190.0

12.6

17.8

183.0

12.7

17.9

1750

12.8

18.0

168.0

12.9

18. 1

163.0

13.0

18.2

158.0

13 I

18.3

1530

13.2

18.4

148.0

133

18.5

143 0

134

18.6

138.0

135

18.7

1350

13.6

18.8

130.0

13-7

18.9

128.0

13-8

19.0

125.0

13-9

19. 1

122.5

14.0

19.2

120.0

14.1

193

II7-5

14.2

19.4

115. 0

14-3

19-5

112. 5

14.4

19.6

110. 0

14-5

19.7

107-5

14.6

19.8

105.0

147

19.9

102.5

14.8

20.0

100. 0

14.9

20.1

98.3

150

20.2

96 -5

151

20.3

94.8

15-2

20.4

93 0

153

20.5

91 5

iS-4

20.6

90.0

iSS

20.7

88.5

15-6

20.8

873

iS-7

20.9

85.8

15-8

21.0

845

159

21 . 1

83.3

16.0

21 .2

82.0

16.1

21-3

81.0

16.2

21.4

80.0

1 1

16.3

21-5

78.8

16.4

21 .6

77.8

16. 5

21.7

76.8

16.6

21.8

75-8

16.7

21 .9

74.8

15-8

22.0

73-8

16.9

7.VO

17.0

2l6

AIR, WATER, AND FOOD

TABLE VIII

TABLE OF HARDNESS, SHOWING THE PARTS OF CALCIUM CARBONATE (caCOa) IN

1,000,000 FOR EACH TENTH OF A CUBIC CENTIMETER

OF SOAP SOLUTION USED

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

cu. cm.

0.0

1.6

3-2

I.O

7-9

9-5

II .1

12.7

14-3

15-6

16.9

18.2

2.0

22.1

234

24.7

26.0

27-3

28.6

29-9

31.2

35-1

364

37-7

390

40.3

41.6

42.9

44-3

4.0

48.6

50.0

51-4

529

54-3

55-7

S7-I

58.6

62.9

643

65.7

67.1

68.6

70.0

71-4

72.9

6.0

77.1

78.6

80.0

81.4

82.9

84-3

85-7

87.1

7.0

91.4

92.9

94-3

95-7

97.1

98.6

100. 0

101.5

8.0

103

104

106.0

107.5

109.0

no. 5

112. 0

"3-5

115. 0

116. 5

9.0

118

119

121 .1

122.6

124. 1

125.6

127. 1

128.6

130. 1

131. 6

10. 0

133

134

136. 1

137.6

I39-I

140.6

142. 1

143-7

145-2

146.8

II. 0

148

150

151-6

153-2

154-8

156.3

157-9

159 -5

161. 1

162.7

12.0

164

165

167.5

169.0

170.6

172.2

173-8

175-4

177.0

178.6

13.0

180

181

183.3

184.9

186.5

188. 1

189.7

191-3

192.9

194.4

14.0

196

197

199.2

200.8

202.4

204.0

205.6

207.1

208.7

210.3

ISO

211

213

215. 1

216.8

218.5

220.2

221.8

223 -5

225.2

226.9

TABLE IX

FOR CORRECTING THE SPECIFIC GRAVITY OF MILK ACCORDING TO TEMPERATURE
ADAPTED FROM THE TABLE OF VIETH

(Temperature in Degrees Centigrade)

Specific
gravity.

10°

11°

12°

13°

14°

15°

16°

17°

18°

19°

20°

1.025

24.1

24-3

24-5

24.6

24.7

24-9

25-1

25-3

25-4

25-6

25-9

25-1

25-2

25-4

25-5

25-7

25-9

26.1

27.0

26.1

26.2

26.4

26.5

26.7

26.9

27.1

28.0

27.0

27.2

27.4

27-5

27.7

27-9

28.1

29.0

28.0

28.2

28.4

28.5

28.7

28.9

29.1

30.1

29.0

29.1

293

29-5

29.7

29.9

30.1

3I-I

29.9

30.1

30.3

30-4

30.6

30.9

31.2

32.2

30.9

3I-I

31-3

31-4

31-6

31-9

32.2

33-2

318

32.0

32-3

32-4

32.6

329

33-2

34-2

32.7

330

33-2

33-4

33-6

33-9

34-2

35-2

33-6

33-9

34-1

34-4

34-6

34-9

35-2

36.2

Directions. — Find the observed gravity in the left-hand column. Then, in
the same line, and under the observed temperature, will be found the corrected
reading.

APPENDIX A

217

TABLE X

PERCENTAGE OF ALCOHOL FROM THE SPECIFIC GRAVITY AT

- 0 -

D 0

C. (

hehner)

Per cent

Sp.gr.

alcohol

Sp.gr.

alcohol

Sp.gr.

alcohol

is°.s c.

I5°.S C.

15°.S C.

weight.

volume.

weight.

volume.

weight.

volume.

1. 0000

0.00

0.9999

0.05

0.07

0.9959

2.33

2 93

0.9919

4.69

586

O.II

0.13

4-75

5 94

0. 16

0. 20

4.81

6.02

0.21

0,26

4.87

6.10

0.26

0.33

4-94

6.17

0.32

0.40

5.00

6.24

0.37

0.46

5.06

6.32

0.42

0.53

5-12

6.40

0.47

0.60

S19

6.48

053

0.66

5-25

6.55

0.9989

0.58

0 73

0.9949

0.9909

5 31

6 63

0.63

0.79

5-37

6.71

0.68

0.86

5-44

6.78

0.74

0-93

5-50

6.86

0.79

0.99

5 0-6

6.94

0.84

1 .06

5.62

7.01

0.89

113

569

7.09

0-95

1. 19

5-75

7.17

1 .00

1 .26

5-8i

7-25

1 .06

1-34

587

732

0.9979

1. 12

1.42

0 9939

0.9899

5 94

7 40

1. 19

1.49

6.00

7.48

I 25

1-57

6.07

7-57

I-3I

1.65

6.14

7.66

1-37

1-73

6.21

7-74

1.44

1. 81

6.28

7.83

I SO

1.88

6.36

7.92

1.56

1.96

6.43

8.01

1 .62

2.04

6.50

8.10

1 .69

2.12

6.57

8.18

0.9969

I 75

2 20

0.9929

0.9889

6 64

827

1. 81

2.27

6.71

8.s6

1.87

2-35

6.78

8.45

1.94

2-43

6.86

8.54

2.00

2-51

6.93

8.63

2.06

2.58

7.00

8.72

, 3

2. II

2.62

7.07

8.80

2.17

2.72

7.13

8.88

2.22

2.79

7.20

8.96

2.28

2.86

7.27

9.04

2l8

AIR, WATER, AND FOOD

TABLE X. — {Continued)

PERCENTAGE OF ALCOHOL

Per cent

Sp.gr.

ailcohol

alcohol

Sp.gr.

alcohol

1 Sp. gr.

alcohol

15°.5 C.

I5°.S C.

weight.

volume.

weight.

volume.

weight.

volume.

0.9879

7 33

9 13

10.46

12.96

13-77

16.98

9.21

10.54

-05

9.29

10.62

9-37

10.69

9-45

10.77

0.9789

9-54

10.85

9.62

9.70

0.9829

10.92

9.78

II .00

9.86

11.08

II. 15

0.9869

9 95

11.23

10.03

II. 31

10.12

11.38

10.21

11.46

10.30

11-54

0.9779

10.38

II .62

10.47

10.56

0.9819

11.69

10.65

11.77

10 -73

11.85

2,2,

0.9859

10.82

II .92

8
8

79
86

10.91
II .00

5
4

12.00
12.08

14
14

84
93

2
I

15
15

19
19

08
18

11.08

3
2

12.15
12.23

15
15

02
12

5
4
3
2
I
0

9
9
9
9
9
9

00
07

14
21
29
36

II. 17
11.26

11-35
11.44
11.52
11 .61

I
0

0 9809

8
7

12.31
12.38

12.46

12.54
12.62

15
15

21
30

49
58

0.9769

7
6

5
4

15
15
16
16
16

83
92
00
08
15

19
19
19
19
19

49
59
68
78

0.9849

II 70

12.69

11.79

12.77

11.87

12.85

11.96

12.92

12.05

13.00

12.13

13.08

0-9759

12.22

13-15

12.31

12.40

0.9799

13 23

16.

12.49

13-31

13-38

0.9839

12.58

13-46

12.68

13-54

12.77

13.62

12.87

13.69

APPENDIX A

219

TABLE X. — {Continued)

PERCENTAGE OF ALCOHOL

Per cent

Sp.gr.

alcohol

Sp. gr.

alcohol

Sp. gr.

alcohol

IS°.S c.

IS°.5 C.

I5°.5C.

weight.

volume.

weight.

volume.

weight.

volume.

0.9749

17 33

21.29

20.00

24.48

22.62

27 -59

20.39

20.08

21.49

20.17

21-59

20.25

21.69

20.33

21.79

20.42

0.9679

21.89

20.50

21.99

23,

22.09

0.9709

20.58

22.18

20.67

20.75

0.9739

22.27

20.83

22.36

20.92

22.46

21.00

22.55

21.08

22.64

21.15

22.73

21 .23

0.9669

22.82

21.31

22.92

23.01

0 9699

21.38

23 . 10

21 .46

21.54

0.9729

23.19

21 .62

23.28

21.69

23 38

21.77

23 48

21.85

23 58

21 .92

23.68

22 .00

0.9659

23.78

22.08

23.88

23.98

0.9689

22.15

24.08

22.23

22.31

0.9719

24.18

22.38

24.28

22.46

24 38

22.54

220

AIR, WATER, AND FOOD

TABLE XI

EXTRACT IN WINE

Per cent by Weight
(According to Windisch)

Sp.gr.

Ex-

Sp. gr.

Ex-

Sp. gr.

Ex-

Sp.gr.

Ex-

Sp.gr.

E.X-

Sp. gr.

Ex-

tract.

I.OOOO

0.00

1.0200

5.17

I . 0400

10.35

I . 0600

IS. 55

I . 0800

20.78

I. 1000

26.04

I. coos

0.13

1. 0205

5. 30

I. 040s

10.48

I. 060s

15.68

1.0805

20.91

I. 1005

26.17

1. 0010

0.26

I. 0210

S.43

I. 0410

10.61

I. 0610

15.81

I. 0810

21.04

I.IOIO

26.30

l.oois

0.39

I. 0215

5.56

1.041S

10.74

I. 0615

15.94

I. 0815

21.17

1.1015

26.43

I.O020

0.52

I . 0220

5.69

1.0420

10.87

I . 0620

16.07

1.0820

21.31

I . 1020

26.56

I.002S

0.64

1. 0225

5.82

1.042s

11.00

1.062s

16. 21

1.082s

21.44

I . 1025

26.70

1.0030

0.77

1.0230

5. 94

1.0430

II. 13

1.0630

16.33

1.0830

21.57

I . 1030

26.83

1.003s

0.90

1.023s

6.07

I. 0435

11.26

1.0635

16.47

1.0835

21.70

I . 103s

26.96

I . 0040

1.03

1.0240

6.20

I . 0440

11.39

I . 0640

16.60

1.0840

21.83

I . 1040

27.09

1.0045

1. 16

1.0245

6.33

1.0445

11.52

1.0645

16.73

1.084s

21.96

I. 1045

27.22

I . 0050

1.29

1.0250

6:46

1.0450

11.65

1.0650

16.86

1.0850

22.09

I . 1050

27.3s

1.005s

1.42

I. 0255

6.59

1.045s

11.78

1.0655

16.99

1.0855

22.22

I. 1055

27.49

1.0060

i.SS

I . 0260

6.72

1.0460

11.91

I . 0660

17.12

1.0860

22.36

I. 1060

27.62

1.0065

1.68

1.026s

6.85

1.046s

12.04

1.0665

17.2s

1.0865

22.49

I . 1065

27. 75

1.0070

1. 81

1.0270

'6.98

1.0470

12.17

I . 0670

17.38

1.0870

22.62

I . 1070

27.88

1.0075

I 94

1.027s

7:11

1.0475

12.30

1.0675

17.51

1.087s

22.75

I. 1075

28.01

1.0080

2.07

1.0280

7*24

I . 0480

12.43

1.0680

17.64

1.0880

22.88

I . 1080

28.15

1.008s

2.19

I . 0285

J -37

1.048s

12.56

1.0685

17.77

1.088s

23.01

I . 1085

28.28

1.0090

2.32

I . 0290

Vso

I . 0490

12.69

I . 0690

17.90

1.0890

23.14

I. 1090

28.41

1.009s

2.4s

1.029s

7.63

1.0495

12.82

1.069s

18.03

1.089s

23.28

I. 1095

28.54

I. 0100

2.S8

I . 0300

7.76

i.osoo

12.95

1.0700

18.16

1.0900

23.41

I.IIOO

28.67

i.oios

2.71

1.030s

7.89

i.osos

13.08

I. 070s

18.30

1.0905

23.54

i.iios

28.81

I. Olio

2.84

I. 0310

8.02

1.0510

13-21

I. 0710

18.43

I. 0910

23.67

I. mo

28.94

ions

2.97

I. 0315

8.14

1.0515

13.34

I. 0715

18. s6

1.0915

23.80

1.1115

29.07

1. 0120

3 10

1.0320

8.27

1.0520

13.47

1.0720

18.69

1.0920

23.93

1.1120

29.20

I. 0125

3.23

1.032s

8.40

1.0525

13.60

1.0725

18.82

1.092s

24.07

1.1125

29.33

I. 0130

3.36

1.0330

8.53

I . 0530

13.73

1.0730

18.95

1.0930

24.20

1.1130

29.47

I. 0135

3.49

I. 0335

8.66

1.0535

13.86

1.0735

19.08

1.0935

24.33

I.II3S

29.60

I. 0140

3.62

1.0340

8.79

I . 0540

13 99

1.0740

19.21

1.0940

24.46

1.1140

29.73

1.014s

3.7s

1.0,345

8.92

I. 0545

14.12

1.0745

19.34

I. 0945

24. 59

1.1145

29.86

I. 0150

3.87

1.0350

9.05

I. 0550

14.25

1.0750

19.47

1.0950

24.72

i.iiso

29.99

I. 015s

4.00

1.0355

9.18

I.0SS5

14.38

1.0755

19.60

1 . 0955

24.85

l.iiSS

30.13

I. 0160

4.13

1.0360

9-31

1.0560

14. SI

1 . 0760

19.73

1.0960

24.99

1.016s

4.26

1.0365

9.44

1.0565

14.64

1.0765

19.86

1.0965

25.12

I. 0170

4.39

1.0370

9.57

1.0570

14.77

1.0770

20.00

1.0970

25.25

I.0I7S

4.52

I 0375

9 70

I. 057s

14.90

1.077s

20.12

1.097s

25.38

I. 0180

4.6s

I . 0380

9.83

1.0580

15.03

1.0780

20.26

1.0980

25.51

I. 0185

4.78

1.038s

9.96

1.0585

15.16

1.0785

20.39

1.098s

25.64

I. 0190

4.91

1.0390

10.09

1.0590

15.29

1.0790

20.52

1 . 0990

25.78

I 0195

S.04

1.0395

10.22

1.0595

15.42

1.0795

20.65

1.0995

25.91

APPENDIX A

221

TABLE XII

TABLE FOR REDUCING SUGAR CONDENSED FROM THAT OF
MUNSON AND WALKER

(Expressed in milligrams)

a
3

■ X

§0

0
1

sQ.

3 3

u ' —

"5=

4.0

4-5

4.0

5.9

260

117.6

121.4

178.3

203.9

6.2

6.7

9 9

265

120.0

123.9

181. 9

207.9

8.3

8.9

10 9

13.8

270

122.5

126.4

185-4

211. &

10.5

II. 2

14-4

17.8

275

124.9

128.9

188.9

215. &

12,6

13.4

17.8

21.8

280

127.3

131. 4

192.4

219.7

14.8

15.6

21.3

25.7

285

129.8

133 9

196.0

223.7

16.9

17.8

24.8

29.7

290

132.3

136.4

199 5

227.6

19. 1

20.1

28.2

33.7

295

134.7

138.9

203.0

231.6

21.3

22.3

31-7

37.6

300

137.2

141.5

206 6

235. 5

23.5

24.6

35 I

41.6

305

139.7

144.0

210. 1

239. S

25.6

26.8

38.6

45-6

310

142.2

146.6

213.7

243.5

27.8

29.1

42.1

49-5

315

144.7

149 1

217.2

247-4

30.0

31-3

45 5

53-5

320

147-2

15I-7

220.7

251-3

32.2

33-6

49.0

57-5

325

149-7

154-3

224-3

255-3

34-4

35-9

52.5

61.4

330

152.2

156.8

227.8

259-3

36.7

38.2

56.0

65.4

335

154.7

159-4

231.4

263.2

38.9

40.4

59-4

69.3

340

157-3

162.0

234.9

267.1

41. 1

42.7

62 9

73-3

345

159 8

164.6

238.5

271. 1

100

43-3

450

66.4

77.3

350

162.4

167.2

242 0

275.0

105

45.5

47-3

69.8

81.2

355

164.9

169.8

245-6

279.0

47.8

49.6

73.3

85.2

360

167-5

172 5

249 -1

282.9

115

50.0

51.9

76.8

89.2

365

170. 1

175- 1

252-7

286.9

120

52.3

54.3

80.3

93 I

370

172-7

177 7

256.2

290.8

125

54-5

56.6

83.8

97.1

375

175-3

180 -4

2.S9-8

294.8

130

56.8

58.9

87.3

lOI.O

380

177-9

183.0

263-4

298.7

13s

59.0

61.2

90.8

105.0

385

180.5

18s. 7

266.9

302.7

140

61.3

63.6

94.2

109.0

390

183.1

188.4

270.5

306.6

145

63.6

65.9

97.7

112. 9

395

185.7

191 0

274-0

310.6

150

659

68.3

IOI.2

116. 9

400

188 4

193-7

277-6

314.5

ISS

68.2

70.6

104.7

120.8

405

191. 0

196.4

281.1

318.5

160

70.4

73.0

108.2

124.8

410

193.7

199.1

284.7

322.4

16S

72.8

75.3

III. 7

128.8

415

196.3

201.8

288.3

326.3

170

75.1

77.7

115. 2

132.7

420

199 0

204.6

291.9

3.30.3

175

77.4

80.1

118. 7

136.7

425

201.7

207.3

295-4

334-2

180

79.7

82.5

122.2

140.6

430

204.4

210.0

299.0

338.2

185

84.2

84.9

125.7

144.6

435

207.1

212.8

302.6

342.1

190

84.3

87.2

129.2

148.6

440

209.8

215.5

306.2

346.1

195

86.7

89.6

132.7

152. 5

445

212.5

218.3

309.7

350.0

200

89.0

92.0

136.2

156.5

450

215.2

221.1

313 3

353. 9

205

91.4

94.5

139.7

160.4

455

218.0

223.9

316.9

357 9

210

93.7

96 9

143 2

164.4

460

220.7

226.7

320. 5

361.8

215

96.1

99-3

146 7

168.3

46s

223. 5

229.5

324.1

365.8

220

98.4

IOI.7

150.2

172.3

470

226.2

232.3

327.7

369.7

225

100.8

104.2

153-7

176.2

475

229.0

235.1

331.3

3-3.7

230

103.2

106.6

157.2

180.2

480

231.8

237-9

334.8

377.6

235

105.6

109. 1

160.7

184.2

485

234.6

240.8

338.4

381.5

240

108.0

III. 5

164.3

188.1

490

237.4

243.6

342.0

385.5

245

no. 4

114 0

167.8

192. 1

250

112. 8

116 4

171. 3

196.0

255

IIS-2

118. 9

174.8

200.0

222

AIR, WATER, AND FOOD

TABLE XIII

EXTRACT IN BEER-WORT

(According to Schultz and Ostermann)

Specific

Extract.

Specific

Extract.

Specific

Extract. Sp

ecific

Extract.

gravity at

Per cent

gravity at

Per cent

gravity at

Per cent gra

i/ity at

Per cent

IS°C.

by weight.

15° c.

by weight.

15° c.

by weight. i.

°C.

jy weight.

I .0000

0.00

I .0235

6.07

I .0470

11.89 I.

0705

17.59

I . 0005

013

1.0240

6. 19

1.0475

12.01 I.

0710

17.70

I .0010

0.26

1.0245

6.31

I . 0480

12.14 I

0715

17.81

1. 0015

0.39

I .0250

6.44

1.0485

12.26 I

0720

17 93

1.0020

0.52

I .0255

6.58

I . 0490

12.38 I

0725

18.04

1.0025

0.66

I .0260

6.71

I 0495

I 2 . 50 I

0730

18.15

1.0030

0.79

1.0265

6.85

I .0500

12.63 I

0735

18.26

I 0035

0.92

I .0270

6.99

1-0505

12.75 I

0740

18.38

1.0040

I -OS

1.0275

7.12

I. 0510

12.87 I

0745

18.49

1.004s

1. 18

1.0280

7.26

I 0515

12.99 I

0750

18.59

1.0050

1.31

1.0285

7.37

I .0520

13.12 I

0755

1S.70

I 0055

1.44

1.0290

7.48

1-0525

13.24 I

0760

18.81

I . 0060

1.56

1.0295

7.60

1-0530

13.36 I

0765

18.91

1.0065

1.69

I . 0300

7.71

1-0535

13.48 I

0770

19.02

1.0070

1.82

1.0305

7.82

1.0540

13.61 I

0775,

19.12

1.0075

1-95

I. 0310

7-93

I -054s

13-73 I

0780

19.23

I .0080

2.07

1-0315

8.04

I 0550

13.86 I

0785

1933

I . 0085

2.20

1.0320

8.16

1.0555

13.98 I

0790

19.44

I . 0090

2.33

I 0325

8.27

I . 0560

H-ii I

0795

19.56

I .0095

2.46

1.0330

8.40

1-0565

14.23 I

0800

19.67

I .0100

2.58

1-0335

8.53

1.0570

14.36 I

0805

19.79

I. 0105

2.71

1.0340

8.67

1-0575

14.49 I

0810

19.91

I .0110

2.84

I -0345

8.80

1.0580

14.62 I

0815

20.03

I.0115

2.97

1.0350

8.94

1.0585

14-75 I

0820

20. 14

I. 01 20

3.10

I -0355

9.07

1.0590

14.89 I

0825

20. 26

I. 0125

3 23

1.0360

9.21

1.0595

15.02 I

0830

20.37

I. 0130

3-35

I 0365

9.34

I .0600

15-14 I

0835

20.48

I .0135

3-48

1.0370

9-45

I .0605

15-25 I

0840

20.59

I .0140

3.61

I -037s

9-57

I .0610

15.36 I

0845

20.70

I. 0145

3.74

I .0380

9.69

I . 06 1 5

1547 I

0850

20,81

1. 0150

387

1-0385

9.81

I .0620

15-58 I

0855

20.93

1.015s

4.00

1.0390

9.92

I .0625

15.69 I

0860

21.06

I .0160

4.13

1.0395

10.04

I . 0630

15.80 I

0865

21 .19

I. 0165

4.26

I . 0400

10.16

1.0635

15.92 I

0870

21-33

I. 01 70

4-39

I . 0405

10.27

I . 0640

16.03 I

0875

21-43

I. 0175

4-53

I .0410

10.40

1.0645

16.14 I

0880

21-54

I .0180

4.66

I. 0415

10.52

I .0650

16.25 I

0885

21.64

I. 0185

4-79

I .0420

10.65

1.0655

16.37 I

0890

21-75

I .0190

4.93

1.0425

10. -7

I . 0660

16.50 I

0895

21.86

I. 0195

5.06

1.0430

10.90

I .0665

16.62 I

.0900

21.98

I .0200

5.20

1.0435

11.03

I .0670

16.74 I

.0905

22.08

1.0205

5-33

1 .0440

II. 15

1.0675

16.86 I

.0910

22. 19

I .0210

5-45

I .0445

11.28

I . 0680

16.99 I

•0915

22.30

I. 0215

5-57

1.0450

II .40

1.0685

17. II I

.0920

22.41

I .0220

5 -70

1-0455

11.53

I . 0690

17.23 I

•0925

22.52

I .0225

5-82

I . 0460

11.65

I .0695

17.35 I

.0930

22.63

1.0230

5-94

1.0465

11.77

I .0700

17.48 I

.0935

22.73

APPENDIX A

223

TABLE XIII. — {Continued}

EXTRACT IN BEER-WORT

(According to Schultz and Ostermann)

Specific

Extract.

Specific

Extract.

Specific

Extract.

Specific

Extract.

gravity at

Per cent

gravity at

Per cent

gravity at

Per cent

gravity at

Per cent

15° c.

by weight.

15° c.

by weight.

15° C.

by weight.

15° c.

by weight.

1.0940

22.84

1 . 1020

24-53

I .1100

26.27

I.I180

27.88

0945

22.94

1. 1025

24.64

I. I 105

26.37

1.118s

27.98

0950

23 05

I . 1030

24-74

I .1110

26.48

1.1190

28.09

095s

23.16

I -1035

24.85

I.III5

26.58

1.1195

28.19

0960

23.27

I . 1040

24.96

I.II20

26.68

1.1200

28.28

0965

2337

I . 1045

25-07

I .1125

26.79

1 . 1 205

28.38

0970

23-48

I. 1050

25 . 18

I. 1 130

26.89

I .1210

28.48

0975

23 -59

I 1055

25.29

I-II35

26.99

1.1215

28.58

0980

23.69

I . 1060

25-40

I.II40

27.09

1 .1220

28.68

0985

23.80

1-1065

25-50

I-II45

27.19

1 .1225

28.78

0990

23.90

I . 1070

25.61

I . II50

27.29

1.1230

28.88

0995

24.01

1.107s

25-71

I-II55

27.38

I-I235

28.98

1000

24. II

I . 1080

25-82

I . I160

27.48

1.1240

29.08

1005

24.21

1-1085

25-93

I.I165

27-58

I -1245

29.18

1010

24.32

I . 1090

26.05

I .1170

27.68

1.1250

29.28

1015

24 -43

I. 1095

26. 16

I-II75

27-78

I-I255

29.38

224

AIR, WATER, AND FOOD

LOGARITHMS

NUMBERS

Natural

Proportional parts.

num-

bers.

I
4

2
8

5
21

0000

0043

0086

0128

0170

0212

0253

0294

0334

0374

0414 0453 '040 2

0531

0569

0607

0645

0682

0719

0755

0792 0828,0864

0899

0934

0969

1004

1038

1072

1 106

1139

1173

1206

1239

1271

1303

1335

1367

1399

1430

1461

1492

1523

1553

1584

1614

1644

1673

1703

1732

1761

1790

1818

1847

1875

1903

1931

1959

1987

2014

2041

2068

209s

2122

2148

2175

2201

2227

2253

2279

2304

2330

2355

2380

2405

2430

2455

2480

2504

2529

2553

2577

2601

2625

2648

2672

2695

2718

2742

2765

2788

2810

2833

2856

2878

2900

2923

294s

2967

2989

3010

3032

3054

3075

3096

3118

3139

3160

3181

3201

3222

3243

3263

3284

3304

3324

3345

3365

3385

3404

3424

3444

3464

3483

3502

3522

3541

3560

3579

3598

3617

3636

3655

3674

3692

3711

3729

3747

3766

3784

3802

3820

3838

3856

3874

3892

3909

3927

3945

3962

3979

3997

4014

4031

4048

4065

4082

4099

4116

4133

4150

4166

4183

4200

4216

4232

4249

4265

4281

4298

4314

4330

4346

4362

4378

4393

4409

4425

4440

4456

4472

4487

4502

4518

4533

4548

4564

4579

4594

4609

4624

4639

4654

4669

4683

4698

4713

4728

4742

4757

4771

4786

4800

4814

4829

4843

4857

4871

4886

4900

4914

4928

4942

4955

4969

4983

4997

501 1

5024

5038

5051

5065

5079

5092

5105

5119

5132

5145

5159

5172

5185

S198

5211

5224

5237

5250

5263

5276

5289

5302

5315

5328

5340

5353

5366

5378

5391

5403

5416

5428

5441

5453

5465

5478

5490

5502

5514

5527

5539

5551

5563

5575

5587

5599

5611

5623

5635

5647

5658

5670

5682

5694

5705

5717

5729

5740

5752

5763

5775

5786

5798

5S09

5821

5832

5843

5855

5866

5877

5888

5899

59"

5922

5933

5944

5955

5966

5977

5988

5999

6010

6021

6031

6042

6053

6064

6075

6085

6096

6x07

6117

6128

6138

6149

6160

6170

6180

6191

6201

6212

6222

6232

6243

6253

6263

6274

62S4

6294

6304

6314

6325

6335

6345

6355

6365

6375

6385

6395

6405

6415

6425

6435

6444

6454

6464

6474

6484

6493

6503

6513

6522

6532

6542

6551

6561

6571

6580

6590

6599

6609

6618

6628

6637

6646

6656

6665

6675

6684

6693

6702

6712

6721

6730

6739

6749

6758

6767

6776

6785

6794

6803

6812

6821

6830

6839

6848

6857

6866

6875

6884

6893

6902

69 1 1

6920

6928

6937

6946

6955

6964

6972

6981

6990

6998

7007

7016

7024

7033

7042

7050

7059

7067

7076

7084

7093

7101

7110

7118

7126

7135

7143

7152

7160

7168

7177

7185

7193

7202

7210

7218

7226

7235

7243

7251

7259

7267

7275

7284

7292

7300

7308

7316

7324

7332

7340

7348

7356

7364

7372

7380

7388

7396

APPENDIX A

225

LOGARITHMS

NUMBERS

Natura

Proport

onal parts.

num-

7412

2
7419

7
7459

bers.

I 234

567 8 9

7404

7427

7435

7443

7451

7466

7474 122,

(45567

7482

7490

7497

7505

7513

7520

7528

7536

7543

7551 122.

(45567

7559

7566

7574

7582

7589

7597

7604

7612

7619

7627 122,

145567

5«

7634

7642

7649

7657

7664

7672

7679

7686

7694

7701 112:

44567

7709

7716

7723

7731

7738

7745

7752

7760

7767

7774 112;

44567

7782

7789

7796

7803

7810

7818

7825

7832

7839

7846 I 2 :

44566

7853

7860

7868

7875

7882

7889

7896

7903

7910

7917 I 1 2 i

44566

7924

7931

7938

7945

7952

7959

7966

7973

7980

7987 I I 2 2

34566

7993

8000

8007

8oi4!8o2i

8028

8035

8041

8048

8055 I I 2 3

3 4 5 S 6

8062

8069

S075

8082

8089

8096

8102

8109

8116

8122 I I 2 3

3 4 S S 6

8129

8136

8142

8149

8156

8162

8169

8176

8182

8189 I I 2 3

34556

S195

8202

8209

8215

8222

8228

8235

8241

8248

8254 I I 2 3

3 4 5 5 6

8261

8267

8274

8280

8287

8293

8299

S306

8312

8319 I I 2 3

34556

8325

8331

8338

8344

8351

8357

8363

8370

8376

8382 1123

34456

8388

839s

8401

8407

8414

8420

8426

8432

8439

8445 I I 2 2

34456

8451

8457

8463

8470

8476

8482

8488

8494

8500

8506 I I 2 2

3 4 4 5 6

8513

8519

8525

8531

S537

8543

8549

8555

S561

8567 I I 2 2

3 4 4 5 5

8573

8579

8585

8591

8597

8603

S609

861S

8621

8627 I I 2 2

3 4 4 5 S

8633

S630

S645

8651

8657

8663

8669

8675

8681

8686 1122

3 4 4 5 5

8692

8698

8704

8710

8716

8722

8727

S733

8739

8745 1122

3 4 4 5 S

8751

8756

8762

8768

8774

8779

8785

8791

8797

8802 I I 2 2

33455

8808

8814

8820

8825

8831

8837

8842

8848

8854

8859 I I 2 2

3 3 4 5 S

8865

8871

8876

8SS2

888 7

8893

8899

S904

8910

8915 I I 2 2

3 3 4 4 5

' 78

8921

8927

8932

S938

8943

8949

8954

8960

8965

8971 I I 2 2

3 3 4 4 5

8976

8982

S987

8993

8998

9004

9009

9015

9020

9026 I I 2 2

3 3 4 4 5

9031

9036

9042

9047

9053

9058

9063

9069

9074

9079 I I 2 2

3 3 4 4 5

9085

9090

9096

9101

9106

9112

9117

9122

9128

9133 1122

3 3 4 4 5

9138

9143

9149

9154

9159

9165

9170

9175

9180

9186 I I 2 2

3 3 4 4 5

9191

9196

9201

9206

9212

9217

9222

9227

9232

9238 I I 2 2

3 3 4 4 5

9243

9248

9253

9258

9263

9269

9274

9279

9284

9289 I I 2 2

3 3 4 4 S

9294

9299

9304

9309

9315

9320

9325

9330

9335

9340 I I 2 2

3 3 4 4 5

9345

9350

9355

9360

9365

9370

9375

9380

9385

9390 I I 2 2

3 3 4 4 5

9395

9400

9405

9410

0415

9420

9425

9430

0435

0440 0 I I 2

23344

9445

9450

0455

9460

0465

0460

9474

9470

9484

9489 0 I I 2

23344

9494

9499

9504

9509

9513

9518

9523

9528

9533

9538 0 I I 2

2 3 3 4 4

9542

9547

9552

9557

9562

9566

9571

9576

9581

9586 0 I I 2

23344

9590

9595

9600

9605

9609

9614

9619

9624

9628

9633 0 I I 2

23344

9638

9643

9647

9652

9657

9661

9666

9671

9675

9680 0 I I 2

2 3 3 4 4

9685

9689

9694

9699

9703

9708

9713

9717

9722

9727 0 I I 2

2 3 3 4 J

9731

9736

9741

9745

9750

9754

9759

9763

9768

9773 0 I I 2

23344

9777

9782

9786

9791

9795

9800

9805

9809

9814

9818 0 I I 2

23344

98 23

9827

9832

9836

9841

9845

Q850

9854

0S59

0S63 0 I I 2

23344

9868

9S72

9877

9881

9886

98QO

0804

0899

9903

90o8 0112

23344

9912

9917

9921

9926

9930

9934

0939

9943

9948

9Q52 0 I I 2

23344

99 9956

9961

9965

9969

9974

9978

9983 J

9987

9991

9996 0 I I 2

23334

226

AIR, WATER, AND FOOD

ANTILOGARITHMS

Loga-
rithms.

Proportional parts.

2
0

O.OO

1000

1002

1005

1007

1009

1012

1014

IO16

1019

1021

O.OI

1023

1026 1028

1030

1033

1035

1038

1040

1042

1045

0.02

1047

1050 1052

1054

1057

1059

1062

1064

1067

1069

0.03

1072

1074

1076

1079

1081

1084

1086

1089

1091

1094

0.04

1096

1099

1102

1 104

II07

1 109

1112

II14

1117

III9

0.05

II22

1125

1127

1 130

II32

"35

1 138

1 140

"43

1 146

0.06

1 148

1151

"53

II56

"59

1161

1 164

I167

1 169

I172

0.07

"75

1178

iiSo

1 183

1186

1 189

1191

"94

"97

"99

0.08

1202

1205

1208

I2II

1213

1216

1219

1222

1225

1227

0.09

1230

1233

1236

1239

1242

1245

1247

1250

1253

1256

O.IO

1259

1262

1265

1268

1271

1274

1276

1279

1282

1285

O.II

1288

1291

1294

1297

1300

1303

1306

1309

1312

1315

0.12

1318

1321

1324

1327

1330

1334

1337

1340

1343

1346

0.13

1349

1352

1355

1358

1361

1365

1368

1371

1374

1377

0. 14

1380

1384

1387

1390

1393

1396

1400

1403

1406

1409

015

1413 1416

1419

1422

1426

1429

1432

1435

1439

1442

0. 16

1445 1449

1452

1455

1459

1462

1466

1469

1472

1476

0.17

147911483

i486

1489

1493

1496

1500

1503

1507

1510

0.18

151411517

1521

1524

1528

1531

1535

153S

1542

1545

0.19

1549

1552

1556

1560

1563

1567

1570

1574

1578

1581

0.20

1585

1589

1592

1596

1600

1603

1607

1611

1614

1618

0.21

1622

1626

1629

1633

1637

1641

1644

1648

1652

1656

0.22

1660

1663

1667

167I

1675

1679

1683

1687

1690

1694

0.23

1698

1702

1706

I7IO

1714

1718

1722

1726

1730

1734

■2

0.24

1738

1742

1746

1750

1754

1758

1762

1766

1770

1774

0.25

1778

1782

1786

179I

1795

1799

1803

1807

1811

1816

0.26

1820

1824

1828

1832

1837

1841

1845

1849

1854

1858

0.27

1862

1866

1871

1875

1879

1884

1888

1892

1897

1901

0.28

1905

1910

1914

I919

1923

1928

1932

1936

1941

1945

0.29

1950

1954

1959

1963

1968

1972

1977

1982

1986

1991

0.30

1995

2000

2004

2009

2014

2018

2023

2028

2032

2037

0.31

2042

2046

2051

2056

2061

2065

2070

2075

2080

2084

0.32

2089 2094

2099

2104

2109

2113

2118

2123

2128

2133

0.33

2138

2143

2148

2153

2158

2163

2168

2173

2178

2183

0.34

2188

2193

2198

2203

2208

2213

2218

2223

2228

2234

0.35

2239

2244

2249

2254

2259

2265

2270

2275

2280

5286

0,36

2291

2296

2301

2307

2312

2317

2323

2328

2333

2339

0.37

2344

2350

235s

2360

2366

2371

2377

2382

2388

2393

0.38

2399

2404

2410

2415

2421

2427

2432

2438

2443

2449

0.39

2455

2460

2466

2472

2477

2483

2489

2495

2500

2506

0,40

2512

2518

2523

2529

2535

2541

2547

2553

2559

2564

0.41

2570

2576

2582

2588

2594

2600

2606

2612

2618

2624

0.42

2630

2636

2642

2649

2655

2661

2667

2673

2679

2685

0.43

2692

2698

2704

2710

2716

2723

2729

2735

2742

2748

0.44

2754

2761

2767

2773

2780

2786

2793

2799

2805

2812

0.45

2818

2825

2831

2838

2844

2851

2858

2864

2871

2877

0.46

2884

2891

2897

2904

2911

2917

2924

2931

2938

2944

0.47

2951

2958

2965

2972

2979

2985

2992

2999

3006

3013

0.48

3020

3027

3034

3041

3048

3055

3062

3069

3076

3083

0.49

3090

3097

3105

3II2

3"9

3126

3^33

314I

3H8

3155

APPENDIX A
ANTILOGARITHMS

227

Loga-

Proportional parts.

rithms

8 9 -

I 2

I I

4
3

7
5

0.50

5162

3170

3177

3184

3192

3199

3206

3214

3221

3228

0-51

3236

3243

3251

3258

3266

3273

3281

3289

3296

3304

I 2

0.52

33^^

3319

3327

3334

3342

3350

3357

3365

3373

3381

I 2

053

3388

3396

3404

3412

3420

3428

3436

3443

3451

3459

I 2

0.54

3467

3475

3483

3491

3499

3508

3516

3524

3532

3540

I 2

0.55

3548

3S5'J

3565

3573

3581

3589

3597

3606

3614

3622

I 2

0.56

3631

3639

3648

3656

3664

3673 3681

3690

3698

3707

I 2

0.57

3715

3724

3733

3741

3750

3758

3767

3776

3784

3793

I 2

0.58

3802

3811

3819

3828

3837

3846

3855

3864

3873 3882

I 2

0-59

3890

3899

3908

3917

3926

3936

3945

3954

3963 3972

I 2

0.60

3981

3990

3999

4009

4018

4027

4036

4046

4055

4064

I 2

0.61

4074

4083

4093

4102

4111

4121

4130

4140

4150

4159

I 2

0.62

4169

4178

4188

4198

4207

4217

4227

4236

4246

4256

I 2

0.63

4266

4276

4285

4295

4305

4315

4325

4335

4345

'355

I 2

0.64

4365

4375

4385

4395

4406

4416

4426

4436

4446

4457

I- 2

0.65

4467

4477

4487

4498

4508

4519

4529

4539

4550

4560

I 2

0.66

4571

4581

4592

4603

4613

4624

4634

4645

4656

4667

I 2

0.67

4677

4688

4699

4710

4721

4732

4742

4753

4764

4775

I 2

0.68

4786

4797

4808

4819

4831

4842

4853

4864

4875

4887

I 2

0.69

4898

4909

4920

4932

4943

4955

4966

4977

4989

5000

I 2

0. 70

5012

5023

5035

5047

5058

5070

5082

5093

5105

5117

I 2

0.71

5129

5140

5152

5164

5176

5188

5200

5212

5224

5236

I 2

0.72

5248

5260

5272

5284

5297

5309

5321

5333

5346

5358

1 2

0.73

5370

5383

5395

5408

5420

5433

5445

5458

5470

5483

I 3

0.74

5495

5508

5521

5534

5546

5559

5572

5585

5598

5610

I 3

0.75

5623

5636

5649

5662

5675

5689

5702

5715

5728

5741

I 3

0.76

5754

576S

5781

5794

5808

5821

5834

5848

5861

5875

I 3

0.77

5888

5902

5916

5929

5943

5957

5970

5984

5998

6012

I 3

0.78

6026

6039

6053

6067

6081

6095

6109

6124

6138 6152 1

I 3

0.79

6166

6180

6194

6209

6223

6237

6252

6266

6281

629s

I 3

0.80

6310

6324

6339

6353

6368

6383

6397

6412

6427

6442

I 3

0.81

6457

6471

6486

6501

6516

6531

6546

6561

6577

6592

2 3

0.82

6607

6622

6637

6653

6668

6683

6699

6714

6730

6745

2 3

0.83

6761

6776

6792

6808

6823

6839

6855

6871

6887

6902

2 3

0.84

6918

6934

6950

6966

6982

6998

7015

7031

7047

7063

2 3

0.8s

7079'

7096

7112

7129

7145

7161

7178

7194

7211

7228

2 3

0.86

7244

7261

7278

7295

73"

7328

7345

7362

7379

7396

2 3

0.87

7413

7430

7447

7464

7482

7499

7516

7534

7551

7568

2 3

0.88

7586

7603

7621

7638

7656

7674

7691

7709

7727

7745

2 4

0.89

7762

7780

7798

7816

7834

7852

7870

7889

7907

7925

2 4

0.90

7943

7962

7980

7998 8017

8035

8054

8072

8091

8110

2 4

0.91

8128

S147

8166

8185 S204

8222 8 24 1

S260

8279 8299

2 4

0.92

8318

S337

S356

83758305

8414S433

8453

8472^8492

2 4

0.93

8511

8531

8551

8570,8590

8610 S630

86^0

8670 S690

2 4

0.94

8710

8730

8750

8770,8790

8810 S83 1

885 1

88 7 2 8892

2 4

005

8913

8933

8954

89748995

9016 9036

9057

9078 9099

2 4

0.96

9120

9141

9162

9183 9204

92269247

9268

9200 93 1 1

2 4

0.97

93 ^ 3

9354

9376

9397 0419

0441 0462

9484

95060528

2 4

0.9S

955°

0572

9594

9616 9638

9661 9683

9705

9727 9750

2 4

0.99

9772

9795

9817

9840 9863

9886 9908

9931

9954 9977

2 5

APPENDIX B

REAGENTS

Air Analysis

Pettenkofer Method. — Barium Hydroxide. — A solution con-
taining about 4 grams of BaO and 0.2 gram of BaCl2 to the liter,
(i c.c. = I mg. CO2, approximately.):

Sulphuric Acid. — Dilute 45.45 c.c. of normal sulphuric acid
to one Hter. (i c.c. = i mg. CO2.) To standardize the solu-
tion measure 25 c.c. into a weighed platinum dish, add dilute
ammonia-water in slight excess, evaporate to dryness on the
water-bath, and dry at 120° C. to constant weight.

Standard Lime-water. — (For Popular Tests.) — Shake one
part of freshly slaked lime with 20 parts of distilled water for
twenty minutes and let the solution stand overnight or until
perfectly clear. This solution should be very nearly equiva-
lent to the above standard sulphuric acid. To a liter of
distilled water add 2.5 c.c. of a solution of 0.7 gram of phenol-
phthalein in 100 c.c. of 50 per cent alcohol and add lime-water
drop by drop until a slight permanent pink color is produced.
Then add 6.3 c.c. of the above calcium hydroxide solution. The
resulting solution is the standard lime-water used for the tests.

Water Analysis

For Ammonia. — Water Free from Ammonia. — The ammonia-
free water used in this laboratory is made by redistilling distilled
water from a solution of alkaline permanganate in a steam-heated
copper still. Only the middle portion of the distillate is collected.
Oftentimes the distillate from a good spring-water may be used.

Nessler's Reagent. — Dissolve 61.750 grams KI in 250 c.c.
distilled water and add a cold solution of HgCl2 which has been
saturated by boiling with an excess of the salt and allowing it

228

APPENDIX 229

to crystallize out. Add the HgClo cautiously until a slight per-
manent red precipitate (Hglo) appears. Dissolve this slight
precipitate by adding 0.750 gram powdered KI. Then add
150 grams of KOH dissolved in 250 c.c. of water. Make up to
a liter and allow it to stand over night to settle. This solution
should give the required color with ammonia within five minutes,
and should not precipitate within two hours.

Alkaline Permanganate. — Dissolve 233 grams of the best
stick potash in 350 c.c. of distilled water. Filter this strong
solution, if necessary, through a layer of glass wool on a por-
celain filter-plate. Dilute with 700 to 750 c.c. of distilled water
to a specific gravity of 1.125, add 8 grams of potassium per-
manganate crystals, and boil down to one liter to free the solution
from nitrogen. Each new lot of reagent must be tested before
being used, but when the chemicals used are all good there
should be no correction needed for ammonia in the solution.

Standard Anwionia Solution. — Dissolve 3.82 grams chemi-
cally pure NH4CI in a liter of water free from ammonia. This
is the strong solution from which the standard solution is
made by diluting 10 c.c. to a liter with water free from am-
monia. One cubic centimeter of the standard solution =
o.ooooi gram nitrogen. This solution, like the nitrite standard
and other dilute solutions, must be preserved in sterilized bot-
tles protected from dust and organic matter.

For Nitrites. — Standard Nitrite Solution. — The pure silver
nitrite used in making this solution is prepared by the double
decomposition of silver nitrate and potassium nitrite, and re-
peated crystallizations from water of the rather difficultly solu-
ble silver nitrite, i.i grams of this silver nitrite are dissolved
in nitrite-free water, the silver completely precipitated by the
addition of the standard salt solution used in the determination
of chlorine, and the solution made up to i liter. 100 c.c. of this
strong solution are diluted to i liter, and 10 c.c. of this last
solution again diluted to i liter. The final solution is the one
used in preparing standards, i c.c. = o.ooooooi gram nitrogen.

Sulphanilic Acid. — Dissolve 3.3 grams sulphaniHc acid in

230 APPENDIX

750 c.c. of water by the aid of heat, and add 250 c.c. glacial
acetic acid.

NapJdhylamine Acetate. — Boil 0.5 gram of a-naphthylamine
in 100 c.c. of water in a small Erlenmeyer flask for about five
minutes, filter through a plug of washed absorbent cotton, add
250 c.c. glacial acetic acid, and dilute to i liter.

For Nitrates. — Standard Nitrate Solution. — Dissolve 0.720
gram of pure recrystallized KNO3 in i liter of water. Evapo-
rate 10 c.c. of this strong solution cautiously on the watci-bath,
moisten quickly and thoroughly with 2 c.c. of phenol-disul-
phonic acid, and dilute to i liter for the standard solution.
I c.c. — o.oooooi gram nitrogen.

Phenol-disulphonic Acid. — Heat together 3 grams synthetic
phenol with 37 grams pure, concentrated H2SO4 in a boiling
water-bath for six hours.

Potassium Hydroxide. — 30 per cent.

For Kjeldahl Process. — Sulphuric Acid. — Sp. gr. 1.84.
This should be free from nitrogen. May be obtained from
Baker and Adamson, Easton, Pa.

Potassium Hydroxide. — Dissolve 350 grams of the best stick
potash in 2.25 liters of water and boil down to something less
than a liter with 3 grams of permanganate crystals. When
cold, dilute to a liter with water free from ammonia.

For Chlorine. — Salt Solution. — Dissolve 16.48 grams of
fused NaCl in a liter of distilled water. For the standard
solution dilute 100 c.c. of this strong solution to i liter, i c.c. =
0.00 1 gram chlorine.

Silver Nitrate. — Dissolve about 2.42 grams of AgNOs (dry
crystals) in i liter of chlorine-free water, i c.c. = 0.0005 gram
CI, approximately. Standardize against the NaCl solution.

Potassium Chromate. — Dissolve 50 grams neutral K2Cr04 in
a little distilled water. Add enough AgNOs to produce a slight
red precipitate. Filter and make the filtrate up to a liter with
water free from chlorine.

Milk of Alumina for Decolorization. — Dissolve 125 grams of
potash or ammonia alum in a liter of distilled water. Pre-

APPENDIX 231

cipitate the A](0H)3 by the cautious addition of XH4OH.
Wash the precipitate in a large jar by decantation until free from
chlorine, nitrites, and ammonia.

For Hardness. — Slandard Calcium Chloride Solution. — Dis-
solve 0.200 gram of pure Iceland spar in dilute HCl, taking care
to avoid loss by spattering, and evaporate to dryness several
times, to remove the excess of acid. Dissolve the calcium
chloride thus formed in i liter of water.

Slandard Soap Solution. — Dissolve 100 grams of the best
white, dry castile soap in a liter of 80 per cent alcohol. Of this
strong solution dissolve 75 to 100 c.c. in a liter of 70 per cent
alcohol. This solution must have 70 per cent alcohol added to
it until 14.25 c.c. of it give the required lather with 50 c.c. of
the above CaClo solution.

Erythrosine Indicator. — Dissolve o. i' gram of ery throsine in
I liter of water.

Methyl Orange Indicator. — Dissolve o.i gram Aniline Orange,
Merck, (Methyl) or Orange III in a few cubic centimeters of
alcohol and dilute to 100 c.c. with distilled water.

Soda Reagent. — Equal parts of sodium hydroxide and sodium

N
carbonate solutions, the mixture to be approximately —

For Iron. — Standard Solution. — Dissolve 0.7 gram of crys-
tallized ferrous ammonium sulphate in 50 c.c. of distilled water
and add 20 c.c. of dilute sulphuric acid. Warm the solution
slightly and add potassium permanganate until the iron is com-
pletely oxidized. Dilute the solution to one liter. One cubic
centimeter of the standard solution equals o.i mg. Fe.

Potassium Sulphocyanate. — 20 grams per liter.

Hydrochloric Acid. — One part HCI (sp. gr. 1.20) to i part of
water.

Potassium Permanganate. — Five grams K]\In04 in i liter of
water.

For Dissolved Oxygen. — Manganous Sulphate. — 48 grams
of MnS04 . 4 HoO in 100 c.c. of water.

Alkaline Potassium Iodide. — 360 grams of NaOH and 100
grams of KI in i liter of water.

232 APPENDIX

Hydrochloric Acid. — Sp. gr. 1.20.

Potassium Acetate. — 100 grams in 100 c.c. of water.

Sodium Thiosidphate Solution. • Dissolve 2.48 grams of

100

the pure crystallized salt in water and dilute to one liter. Stand-

N
ardize against a - — potassium bichromate solution.
100

For Oxygen Consumed. — Standard Ammonium Oxalate Solu-
tion. — Dissolve 0.888 gram pure ammonium oxalate in i liter
of distilled water. One cubic centimeter is equivalent to 0.000 1
gram oxygen consumed.

Potassium Permanganate Solution. — Dissolve 0.4 gram potas-
sium permanganate in i liter of distilled water and standardize
against the ammonium oxalate solution according to the method
described in the text.

N
For Free Carbonic Acid. — Standard — Sodium Carbonate

Solution.

For Lead. — Standard Lead Solution. — To a strong solution of

lead acetate add a slight excess of H2SO4, filter off and wash the

precipitate. Dissolve it in ammonium acetate solution, made

by neutralizing glacial acetic acid with strong ammonia. Make

up to a known volume and determine the lead in an aliquot

part by precipitating with KoCr^Oy and weighing the lead chro-

mate. Dilute an aliquot part to make a convenient standard,

say about i c.c. = o.ooi gram of Pb.

Food Analysis

Pumice. — Bits of ignited pumice, about the size of a pea,
dropped while hot into water and bottled for use.

Alcohol (for Reichert-Meissl method). — 95 per cent alcohol
redistilled from potassium hydroxide.

Iodine Solution (for Hanus' method) . — This is conveniently
made up according to the directions of Hunt.* Dissolve 13.2
grams iodine in i liter of glacial acetic acid (99 per cent, show-

* J. Soc. Chem. Ind., 21, 1902, 454.

APPENDIX 233

ing no reduction with bichromate and sulphuric acid) . This will
best be done by adding the acetic acid in portions and heating
on the water-bath with frequent shaking. To the cold solution
add enough bromine to double the halogen content, as shown
by titration. Three cubic centimeters of bromine is sufficient.
A slight excess of iodine is not detrimental.

Anhydrous Ether. — Wash ordinary ether several times with
distilled water and add soUd caustic potash until most of the
water has been removed. Then add small pieces of clean
metallic sodium until there is no further evolution of hydrogen
gas. The ether thus prepared should be kept over metallic
sodium and a tube of calcium chloride should be inserted in the
stopper, in order to allow the escape of any accumulated gas.

Potassium Sulphide. — Dissolve 40 grams of the crystallized
salt in I liter of water and filter through glass wool.

Potassium Hydroxide (for Kjeldahl process). — Dissolve 700
grams of the best quality of stick potash in water and dilute to
I liter.

Basic Lead Acetate. — Boil for half an hour 440 grams of lead
acetate and 264 grams of litharge in 1500 c.c. of water. Cool
and dilute to 2 liters. Allow to settle and siphon off the clear
liquid. (Specific gravity about 1.27, containing about 35 per
cent of the basic salt.)

Ferric Alum. — Dissolve 2 grams of ferric alum in 100 c.c. of
water, boil the solution until a precipitate appears, and filter.

Fehlings Solution. — {a) Dissolve 69.28 grams of C.P. crys-
tallized copper sulphate, carefully dried between blotting-paper,
in water and make up to i liter, including i c.c. of strong sul-
phuric acid: {h) Dissolve 346 grams of sodium potassium tar-
trate and 100 grams of sodium hydroxide in water and make
up to a Hter.

BIBLIOGRAPHY

AIR

The following list contains the more important books and
articles of recent publication.

Barker, A. H. The Theory and Practice of Heating and Ventilation. The
Carton Press, London, 1912.

Greene, A. M. The Elements of Heating and Ventilation. John Wiley & Sons,
New York, 1913.

Hammarsten-Mandel. a Text Book of Physiological Chemistry. John
Wiley & Sons, New York, 1908.

Hoffman, J. D. Handbook for Heating and Ventilating Engineers. McGraw-
Hill Book Co., New York, 1913.

Macfie, Ronald C. Air and Health. Methuen & Co., London, 1909.

Richards, Ellen H. Conservation by Sanitation. John Wiley & Sons, New
York, 191 1.

Rosenau, M. J. Preventive Medicine and Hygiene. Appleton, New York,

1913-

Shaw, W. W. Air Currents and the Laws of Ventilation. University Press,
Cambridge, Eng., 1907.

SoPER, J. A. Air and Ventilation in Subways. John Wiley & Sons, New
York, 1908.

Talbot, Marion. House Sanitation. Whitcomb & Barrows, Boston, 1913.

Standard Methods for the Examination of Air. American Public Health Asso-
ciation, Boston, 1910.

Affleck. Ventilation of Gymnasia. Am. Phys. Ed. Rev., 1912.

Air Supply and Ventilation Number. Am. J. Pub. Health, Nov., 1913, 3,
pp. 1123-1210.

Crowder. a Study of the Ventilation of Sleeping Cars. Arch. Intern. Med.,
1911, 7, pp. 85-133.

Jordan and Carlson. Ozone: Its Bactericidal, Physiologic and Deodorizing
Action. J. Am. Med. Assn., 1913, 61, p. 1007.

McCuRDY. Recirculated Air. Am. Phys. Ed. Rev., 1913, Dec.

Norton. Ventilation of Sleeping Cars. Science Conspectus, 191 2, 2, pp.
79-82.

Transactions of the 15th International Congress of Hygiene and Demography.
1913, Vol. 2, Pt. II.

Ventilation Symposium. J. Ind. Eng. Chem., 1914, 6, p. 245.

Vosmaer. Industrial Uses of Ozone. J. Ind. Eng. Chem., 1914, 6, p. 229.

Winslow & Kligler. a Quantitative Study of Bacteria in City Dust. Am.
J. Pub. Health, 191 2, 2, p. 663.

234

BIBLIOGRAPHY 235

WATER

The following list contains the most important recent books
on water, from a sanitary standpoint.

Don, J. & Chisholm, J. Modern Methods of Water Purification. 2nd Ed.,
Longmans, Green & Co., New York, 1913.

Fuller, M. L. Domestic Water Supplies for the Farm. John Wiley & Sons,
New York, 1912.

Gerhard, W. P. The Sanitation, Water Supply and Sewage Disposal of
Country Houses. D. Van Nostrand Co., New York, 1909.

Hazen, Allen. The Filtration of Public Water Supplies. 3rd Ed., John
Wiley & Sons, New York, 19 10.

Hazen, Allen. Clean Water and How to Get It. 2nd Ed., John Wiley &
Sons, New York, 19 14.

Mason, W. P. Examination of Water. 4th Ed., John Wiley & Sons, New
York, 1912.

Mason, W. P. Water Supply. John Wiley & Sons, New York, 1909.

Prescott, S. C. and Winslow, C. E. A. Elements of Water Bacteriology.
3rd Ed., John Wiley & Sons, New York, 1913.

RiDEAL, S. Water and Its Purification. Lockwood & Son, London, 1902.

Stocks, H. B. Water Analysis. Griffin & Co., London, 1912.

Thresh, J. C. The Examination of Waters and Water Supplies. 2nd Ed., P.
Blackiston's Son & Co., Philadelphia, 1913.

Thresh, J. C. A Simple Method of Water Analysis. 7th Ed., Churchill,
London, 191 2.

TiLLSMAN, J. Translation by H. S. Taylor. Water Purification and Sewage
Disposal. D. Van Nostrand Co., New York, 1913.

Whlpple, G. C. The Microscopy of Drinking Water. 3rd Ed., John Wiley
& Sons, New York, 1914.

Whipple, G. C. The Value of Pure Water. John Wiley & Sons, New York,
1907.

Annual Reports, Massachusetts State Board of Health, 1879 to 191 2.

Reports of the Metropolitan Water Board, New York City.

Reports of the Royal Commission on Sewage Disposal, England.

FOOD

Only the general books and bulletins published since 1890
which are most available to the student are given here. A de-
tailed list of all important references to food will be found at
the end of each chapter in Leach's Food Inspection and Analysis.

Allen, A. H. Commercial Organic Analysis. 4th Ed., Blakiston, Phila.,
1911.

Bailey, E. H. S. Sanitary and Applied Chemistry. Macmillan, New York,
1906.

236 BIBLIOGRAPHY

Blyth, a. W. and M. W. Foods, their Composition and Analysis. Griffin,
London, 1909.

Farrington, E. H., and Woll, F. W. Testing Milk and Its Products. Men-
dota Book Co., Madison, Wis., 1908.

GiRARD, C. and Dupre, A. Analyse des Matieres Alimentaires. 2d Ed.,
Dunod, Paris, 1904.

Hutchison, R. Food and Dietetics. William Wood, New York, 1908.

KoNiG, J. Die Menschlichen Nahrungs = u. Genussmittel. Springer, Berlin,
1904.

. Die Untersuchung landwirtschaftlich und gewerblich wichtiger Sto£fe.

Parey, Berlin, 191 1.

Leach, A. E. Food Inspection and Analysis. Wiley, New York, 1909.

Leffmann, H. and Beam, W. Food Analysis. Blakiston, Phila., 1905.

Lewkowitsch, J. Oils, Fats and Waxes. Macmillan, New York, 1909.

Mitchell, C. A. Flesh Foods. Griffin, London, 1900.

Moor, C. G. Standards for Food and Drugs. Bailliere, Tindall & Co.x, London,
1902.

Norton, A. P. Food and Dietetics. School of Home Economics, Chicago,
1907.

Olsen, J. C. Pure Food. Ginn & Co., Boston, 191 1.

Pearmain, T. H., and Moor, C. G. The Analysis of Food and Drugs. Bailliere,
Tindall & Cox, London, 1897.

Richards, E. H. The Cost of Food. Wiley, New York, 1901.

. Food Materials and their Adulterations. Home Science Pub. Co.,

Boston, 1908.

Richmond, H. D. Dairy Chemistry. London, 18S9.

Rupp, G. Die Untersuchung von Nahrungsmitteln. Winter, Heidelberg, 1900.

Sherman, H. C. Chemistry of Food and Nutrition. Macmillan, New York,
1911.

. Organic Analysis. Macmillan, New York, 191 2.

Snyder, H. Human Foods. Macmillan, New York, 1908.

Van Slyke, L. L. Testing Milk and Milk Products. Orange Judd, New York,
1911.

Wiley, H. W. Principles and Practice of .Agricultural Analysis. Vol. III.
Chem. Pub. Co., Easton, Pa., 1S97.

. Foods and their Adulteration. Blakiston, Phila., 1911.

The following bulletins of the United States Department of
Agriculture will also be found useful for study or reference on
the general question of food :

Office of Experiment Stations, Bulletins

No. 9. Fermentations of Milk. 1892.

ir. Analyses of American Feeding Stuflfs. 1892.

21. Chemistry and Economy of Food. 1895.

25. Dairy Bacteriology. 1895.

BIBLIOGRAPHY 237

28. (Rev. Ed.) Chemical Composition of American Food Materials. 1895.

29. Dietary Studies at the University of Tennessee. 1896.

31. Dietary Studies at the University of Missouri. 1896.

32. Dietary Studies at Purdue University. 1896.

34. Carbohydrates of Wheat, Maize, Flour, and Bread. 1896.

35. Food and Nutrition Investigations in New Jersey. 1896.

37. Dietary Studies at the Maine State College. 1897.

38. Dietary Studies — Food of the Negro in Alabama. 1897.
40. Dietary Studies in New Mexico. 1897.

43. Composition and Digestibility of Potatoes and Eggs. 1897.

44. Metabolism of Nitrogen and Carbon in the Human Organism. 1897.

45. A Digest of Metabohsm Experiments. 1897.

46. Dietary Studies in New York City. 1898.

52. Nutrition Investigations in Pittsburgh, Pa. 1898.

53. Nutrition Investigations at the University of Tennessee. 1898.

54. Nutrition Investigations in New Mexico. 1898.

55. Dietary Studies in Chicago. 1898. .

63. Experiments on the Conservation of Energy in the Himian Body.
1899.

66. Creatin and Creatinin. 1899.

67. Bread and Bread Making. 1899.

69. Experiments on the Metabolism of Matter and Energy in the Human

Body. 1899.

71. Dietary Studies of Negroes. 1899.

75. Dietar>' Studies of University Boat Crews. 1900.

84. Nutrition Investigations at the California Agr. Expt. Station. 1900.

85. Investigations on the Digestibility and Nutritive \'alue of Bread. 1900.
89. Effect of Muscular Work on Digestion of Food and Metabolism of

Nitrogen. 1901.
91. Nutrition Investigations at the University of Illinois, etc. 1901.
98. Effect of Severe and Prolonged Muscular Work on Food Consumption

Digestibility, and Metabolism. 1901.

101. Studies on Bread and Bread IMaking. 1901.

102. Losses in Cooking Meat. 1901.

107. Nutrition Investigations among Fruitarians and Chinese. 1901.

109. Metabolism of IMatter and Energj- in the Human Body. 1902.

1x6. Dietary Studies in New York City. 1902.

117. Effect of Muscular Work upon Digestibility of Food and Metabolism

of Nitrogen. 1902.

121. Metabolism of Nitrogen, Sulphur, and Phosphorus in the Human

Organism. 1902.

126. Digestibility and Nutritive Value of Bread. 1903.

129. Dietary Studies: Boston and other Places. 1903.

132. Further Investigations among Fruitarians. 1903.

152. Dietary Studies with Harvard L^niversity Students.

162. Studies on Influence of Cooking on Nutritive Value of Meats.

227. Calcium, Magnesium and Phosphorus in Food and Nutrition.

238 BIBLIOGRAPHY

Btireaii of Chemistry, Bulletins

No. 13. Foods and Food Adulteration — (Ten Parts).

45. Analyses of Cereals.

50. Composition of Maize.

59. Composition of American Wines.

61. Pure Food Laws of Foreign Countries.

66. Fruits and Fruit Products.

69. Foods and Food Control.

72. American Wines at Paris Exposition of 1900.

77. Olive Oil and Its Substitutes.

84. Influence of Food Preservatives and Artificial Colors on Digestion and

Health.

100. Some Forms of Food Adulteration and Simple Methods for their De-
tection.

107. Official and Provisional Methods of Analysis.

no. Chemical Analysis and Composition of American Honeys.

114. Meat Extracts and Similar Preparations.

115. Effects of Cold Storage on Eggs, Quail and Chickens.

120. Feeding Value of Cereals.

122. Annual Proceedings A. O. A. C.

132. Annual Proceedings A. O. A. C.

137. Annual Proceedings A. O. A. C. **

152. Annual Proceedings A. O. A. C.

162. Annual Proceedings A. O. A. C.

164. Graham Flour.

Fanners^ Bulletins

No. 23. Foods: Nutritive Value and Cost. 1894.

29. Souring of Milk. 1895.

34. Meats: Composition and Cooking. 1896.

74. Milk as Food. 1898.

85. Fish as Food. 1898.
93. Sugar as Food. 1899.

112. Bread and the Principles of Bread Making. 1900.

121. Beans, Peas, and other Legumes as Food. 1900.
128. Eggs and their Uses as Food. 1901.

131. Household Tests for Detection of Oleomargarine and Renovated Butter.

190 1.

142. The Nutritive and Economic Value of Food. 1901.

182. Poultry as Food.

249. Cereal Breakfast Foods.

252. Maple Sugar and Sirup.

293. Use of Fruit as Food.

332. Nuts and their Uses as Food.

363. Use of Milk as Food.

490. Bacteria in Milk.

BIBLIOGRAPHY 239

Much valuable information will also be found in the regular bulletins and re-
ports of several of the State experiment stations and boards of health, notably
those of Connecticut, North Dakota, Maine, Kansas, New Hampshire, Vermont
and Massachusetts. The "Food Inspection Divisions" and "Notices of Judg-
ment" issued from time to time in the enforcement of the Federal Pure Food
Law also contain interesting information concerning the adulteration of food.

INDEX

Pace

Acid, sulphanilic, reagent 229

sulphuric, reagent for air analysis 228

Adams' method for fat 141

Adulteration, cause of 124

character of 128

definition of 1 24

extent of 128

Air, amount of, required 18

bacteria in 10, 42

collection of samples of 24

composition of expired 11

composition of inspired 9

dust in 9

essential to life 2

humidity of 9, 14

methods of analysis of 21

purification 20

poisonous gases in 10

Alcohol, determination of 191

table 217

Alkalinity, determination of, in water 92

Alum, determination of, in water 95

Alumina, milk of 230

Ammonia, albuminoid, determination of 72

significance of 61

free, determination of 72

significance of 62

free water 228

standard solution of 2 29

Ammonium oxalate solution, standard 232

Analysis, air, methods of 21

water, methods of • 69

accuracy of methods of 59

expression of results of 5S

interpretation of results of 56

Ash, in cereals iSo

in wine 193

of milk 141

241

242 INDEX

Page

Babcock method for fat 142

Bacteria in air, 10

determination of 42

Barometers 21

Basic lead acetate 233

Beer, analysis of 197

Benzoic acid, detection of 196

Bibliography 234

Bleach, use of, in water sterilization 54

Boric acid, detection in milk 154

Breakfast foods 130

Butter, analysis of 165

composition of 162

Federal standard for 164

microscopic examination 178

Butter-fat, composition of 163

Calcium chloride solution, standard 231

Calorie, definition of 117

Calorific value 117

Cane-sugar, detection in milk 150

Caramel in vanilla extracts 204

Carbohydrates, function of 115

Carbon dioxide, allowable amounts in air 17

determination of, in air 27

in water 84

in expired air 11

in inspired air 9

poisonous action of 12

table of weights of cubic centimeters of 209

use as a ventilation test 17

Carbon monoxide in air 10

determination of 40

Carbonaceous matter in water, determination of 85

Casein, determination in milk 146

Cereals, analysis of 180

composition of 181

Chloride of lime, use in water sterilization 54

Chlorides in water, significance of 64

determination of 84

Chlorine, map of normal 65

in water, see chlorides.

Cholera 44

Coal-tar dyes, detection of 194

Cohen and Appleyard method for air analysis 37

Collection of samples of air 24

water 69

INDEX 243

Pace

Color in water, determination of 105

Color, detection in milk 154

Colors in food 132

Comfort II

curve of 16

Cooking, changes caused by 116

Coumarin, determination of 201

Crowd poisoning, theory of 12

Crude fibre 188

Dextrin, determination in cereals 185

Dietaries 1 20

Dust in air g

determination of 23

Electric muflBe furnace 88

Erj'throsine indicator 231

Ether, anhydrous 233

extract in cereals 182

Extract in beer-wort 222

in wine 192

in wine, table 2 20

Fat, determination in milk 141

in cereals 182

Fats, function of 114

Fehlings' solution 233

Ferric alum 233

Ferrous ammoniimi sulphate, standard solution 89, 231

Filter galleries 50

Filters, water 52

Filtration, methods of 52

Fitz shaker 39

Food, composition of 112

definition and uses iii

essential for life 5

materials, composition of iiS

principles 112

values, discussion of 122

Foods, predigested 120

"Fore" milk 13S

Formaldehyde, detection in milk 151

Free acids, in wine 193

Gottlieb method for fat 143

Ground waters 48

Gunning method 1 84

244 INDEX

Page

Hale and IMelia method for dissolved oxygen loi

Hanus method 171

Hardness, acid method for 91

permanent, determination of 93

soap method for 90

table of 216

temporary, determination of 92

total, determination of 94

Hazen's theorem 45

Heat loss from the body, methods of 13

Heat of combustion 117

Hehner value 170

Hehner's acid method for hardness 91

Humidity 9

determination of 22

effect on heat loss of 14

table of relative 210

Hygrometer, hair 22

Ice 55

Imhoff tank 61

Indicator, erythrosine 231

methyl orange 231

potassium chromate 84, 230

Iodine value 171

Hanus solution for 232

Iron in water, determination of 89

standard solution of 231

Jackson's candle turbidimeter 95

Kjeldahl method 183

process for nitrogen in water 78

reagents for 230

Kubel's hot acid method 86

Lead in water, determination of 97

number of vanilla 202

standard solution of 232

Lemon color 207

extract 205

oil, determination of 206

Lime water reagent for air analysis 38, 228

Logwood test for alum in water 95

Loss on ignition, determination of, in water 87

Low's method for alum in water 96

INDEX

245

Pace

Malted cereals, analysis of i8g

Manganese sulphate solution 231

Marsh test for caramel 204

Methyl orange indicator 231

Milk, composition of 136

detection of added water 158

interpretation of analysis 156

serum, examination of 14Q

solids, calculation of 148

sugar, determination of 145

variations in compositions of 137

Mills-Reincke phenomenon 45

Mineral matter in water 65

determination of 87

salts, value in food 116

Misbranding 125

Moisture in cereals 180

see Humidity.

Motion of air, determination of 22

effect on heat loss 14

Naphthylamine acetate solution 80, 230

Nessler reagent 72, 228

Nitrate solution, standard 230

Nitrates in water, determination of 82

significance of 63

Nitrite solution, standard 229

Nitrites in air, determination of 42

in water, determination of 80

significance of 63

Nitrogen cycle 60

in water, determination of total 78

Nitrogen-free extract 184

Nitrogenous substances, function of 113

Nutritive ratio 117

Odor in water, determination of 106

Odors in water, extermination of 48

Oleomargarine 163

Organic matter in water 66

determination of 85

Oxygen consumed, determination of 85

dissolved in water, determination of 100

significance of 66

in expired air 1 1

in inspired air q

table of saturation of water with 103

246 INDEX

Page

Ozone, use in purifying air 20

sterilizing water 54

Pettenkofer method for carbon dioxide ss

Pettersen-Palmquist apparatus 27

Phcnoldisulphonic acid reagent 82, 230

Pollution in wells, methods of tracing 50

past 63

Potassium acetate solution 232

chromate indicator 230

iodide solution, alkaline 231

permanganate, alkaline 73, 229

permanganate solution, standard 232

sulphocyanate reagent 89, 23 1

Preservatives, detection in butter 166

Preservatives in food 132

Protein by Kjeldahl method 182

Proteins in milk 146

Psychrometer 22

Putrescibility test 104

Radiator, platinum 88

Rain fall, average 46

water 45

Rapid methods for air analysis 35

Reagents for air analysis 228

water analysis 228

Reducing sugar, Munson and Walker's table 221

Refractive index 173

Refractometer 174

principle of 175

Reichert-Meissl number 167

Renovated butter, manufacture of 163

Residue on evaporation, determination of 87

Resins, in vanilla 203

Respiration 11

SalicyHc acid, detection of 196

Salt, determination in butter 166

Sanitary science, importance of 2

Sanitation, scope of chemistry of i

Sediment, determination of 108

Self-purification of streams 47

Septic tank 61

Sewage analysis 67, 109

purification required 44

tables of analyses of 213

INDEX 247

Pace

Silver nitrate solution 84, 230

Sl^immed milk, detection of i6i

Soap method for hardness 90

solution, standard 231

Soda reagent 93, 231

Sodium carbonate, detection in milk 154

Sodium chloride solution, standard 84, 230

thiosulphate solution, standard 232

Solids of milk 140

Sonden apparatus for air analysis 27

Specific gravity of milk 139

correction table 216

solids 162

wine 191

Spoon test 177

Standards for ammonia determination 75, 77

Starch, determination of 186

Steam vacuum method for air samples 25

" Strippings " 138

Sulphanilic acid 80, 229

Sulphates in water, determination of 95

table of 215

Sulphites, detection of 198

Sugars in cereal products 185

Surface waters 46

Temperature, determination of 21

effect on heat loss 13

Tests on water, value of 67

Thermometers, wet and dry bulb 22

Turbidimeter for sulphates 95

Turbidity, determination of 108

Turmeric in lemon extract 207

Tj-phoid fever 45

Ultraviolet light for water sterilization 54

Vanilla, adulteration of ^00

determination of 201

extract 190

Vapor tension of water, table of 20S

Ventilation 17

formulae 18

methods of 19

Volatile acids, in wine i94

Walker method for carbon dioxide -8

Water, analytical methods 69

248 INDEX

Page

Water, bacteriological examination of 57, 109

chemical examination of 59, 67

consumption 43

cycle of 45

daily quantity required 4

ground 48

need of 3

physiological action of 43

purification of 51

rain 45

relation to disease 44

safe 56

necessity of 45

samples, collection of 69

sanitary examination of 57

siphon method 24

sterilization of 54

storage of 46

supplies, requirements for 56

surface 46

vapor in air, see Humidity.

waste 43

Waters, table of average composition of 211

table of normal 212

tables of polluted 213

Wells, deep 49

shallow 49

Wine, composition of 190

Winkler method for dissolved oxygen 100

MARGARET CARNEGIE LIBRARY
MILLS COLLEGE

THIS B"OK DUE ON THE LAST DATE
STAMPED BELOW

OCT 1 1

SEMESTER

A OOP 066 795 6

17429

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